MECHANICAL DRAWING 



FOR 



CRAWS HAW AND PHILLIPS 




BooL 



CQEYRIGHT DEPOSHi 



Mechanical Drawing 

FOR 

Secondary Schools 



BY 

FRED D. CRAWSHAW, B.S., M.E. 

PROFESSOR OF MANUAL ARTS, THE UNIVERSITY OF WISCONSIN 



AND 

JAMES D. PHILLIPS, B.S. 

PROFESSOR OF DRAWING AND ASSISTANT DEAN COLLEGE OF ENGINEERING, 
THE UNIVERSITY OF WISCONSIN 



SCOTT, FORESMAN AND COMPANY 
CHICAGO NEW YORK 






Copyright 1916 



SCOTT, FOEESMAN AND COMPANY 




II.A4B8385- 



PREFACE 

Mechanical Drawing is recognized today as an important part 
of a secondary education. For all classes of pupils it serves 
as an important means of developing visualization, strengthen- 
ing the imagination, and forming habits of careful observation 
and perception. For those who will make use of it commercially, 
mechanical drawing is the accepted means of creating a con- 
ventional picture of objects. 

This book analyzes mechanical drawing upon the basis of 
its elements, or natural divisions, such as Perspective Sketch- 
ing, Orthographic Sketching, Pencil Mechanical Drawing, Ink- 
ing, Tracing, and Reproducing. Each one of these divisions is 
treated separately in a chapter. Each chapter organizes the 
division of drawing which it represents. Hence in each chap- 
ter there is presented a progressive series of problems in one 
of the natural divisions of the subject. 

The book contains six chapters and covers the first two years 
of mechanical drawing in Secondary Schools. The first four 
chapters are designed to occupy the time of a class for the 
first year of the two years' course. As there is a large element 
of flexibility in the selection of problems, no one individ- 
ual is expected to solve all problems. The course may be easily 
extended over a period of more than two years, even to three 
or four years, depending upon the number of problems solved, 
whether a part or all of the chapters are included in tlie course, 
and the time devoted to the subject during each year. 

The chapters are arranged in the order in which the divisions 
of drawing are dealt with in commercial draAving room practice. 
Problems, arranged in groups in each chapter, progress in the 
order of their difficulty. Each group of problems is chosen to 

3 



4 MECHANICAL DRAWING 

emphasize the construction of a certain type of line, the use 
of particular instruments, and the application of commonly used 
conventions. It is believed that such a treatment both retains 
and extends all possible educational values attributed to mechan- 
ical drawing. 

In those branches of vocational education which deal with 
industry, mechanical drawing is the means of showing the plan 
of construction or the method of assembling constructed parts. 
Therefore the authors of this book have taken the view that all 
problems presented must represent commercial industrial prac- 
tice. They have selected problems which represent several com- 
mon industrial materials, and the solutions required represent 
the best commercial drawing room practice. Consequently all 
abstract problems have been eliminated except in so far as they 
relate directly to practical problems. This feature, when coupled 
with the one of dwelling upon one division of drawing until a 
complete series of problems in it has been solved, makes the 
book unique in its presentation of unit courses. All of these 
units, when taken together, complete the field of mechanical 
drawing, and each one prepares the student for efficient serv- 
ice in a particular division of the w^hole field of drawing. 

The course presented in this book has the following subject 
matter features: 

1. Every problem represents typical industrial material, 
commercial construction, and the best drawing room practice. 

2. Every chapter presents a complete course in one of the 
natural divisions of drawing. 

3. All problems are arranged in groups depending upon 
the elements in drawing which are involved. The student may 
select or the instructor may assign any one or more of several 
problems in each group, depending upon student ability and 
community interest. This feature of flexibility makes it easy 
to adapt the course at any time to any student in a class and 
to any class in a community by any one or all of three means : 

(a) A selection of problems within a group. 

(b) The addition of problems to any group. 

(e) The elimination of any section of subject matter or of 
any group of problems within a section. 



PREFACE 5 

4. All chapters, when completed in the order in which they 
are arranged, furnish a complete course, both in the subject 
of mechanical drawing and in the field of industry covered in 
secondary education, in which mechanical drawing plays a part. 

The course presented in this book has the following method 
features : 

1. A type problem showing typical conventions and solu- 
tions is furnished for each group of problems. 

2. Numerous data problems, given in the form of freehand 
sketches and finished mechanical drawings, present a standard 
in technique. 

3. Each division in mechanical drawing is analyzed into 
its several elements which are presented in a series of well 
graded, practical problems, involving essential theory and its 
application. 

4 Each division in drawing requires the concentration of 
the student upon one thing at a time until he has a fair mastery 
of both theory and practice. The next division reviews this 
theory and practice in related problems. 

5. Each group of problems in each division in drawing is 
accompanied by explicit instruction and illuminating reading 
for the student, and suggestive demonstration i^aterial for the 
instructor. 

6. Each chapter in the first year's course closes with a series 
of review problems and review questions. 

In order to cover fully the field of mechanical drawing for 
secondary schools and to prepare students for commercial draw- 
ing room practice in the several divisions of the subject, the 
authors have given special attention in the second year of the 
two-year course to such subjects as Sheet Metal Drawing, Archi- 
tectural Drawing, and Machine Drawing. The student who com- 
pletes the work as outlined for the first year will therefore be 
able to devote his attention to. any one of these subjects or to all 
of them depending upon his needs. This element of latitude of 
choice of subject matter makes the book particularly valuable 
in schools where diafting is taught for early vocational use. 

A Teacher's Manual and an Outline of the Course of 
Study are furnished free to teachers using the text. The Manual 



6 PREFACE 

gives brief but pertinent suggestions to assist the instructor. 
The Outline of the Course of Study shows clearly the plan of 
the text and indicates possibilities of modifying it to meet local 
conditions. 

The authors wish to express their appreciation of the co- 
operation of H, D. Orth, Assistant Professor of Drawing and 
Descriptive Geometry, the University of Wisconsin. From the 
very beginning to the end of the book, he has been a co-author 
in its production. 

THE AUTHORS. 



TABLE OF CONTENTS 

CHAPTER ONE 

Page 

Perspective Sketching 9 

CHAPTER TWO 
Orthographic Sketching 66 

CHAPTER THREE 
Pencil Mechanical Drawing 110 

CHAPTER FOUR 
Tracing and Blueprinting 159 

CHAPTER FIVE 

Advanced Drawing 189 

a. Sheet Metal Drawing Problems. 

b. Furniture and Cabinet Drawing Problems. 

c. Machine Drawing Problems. 

d. Architectural Drawing Problems. 

CHAPTER SIX 
Isometric and Cabinet Drawing 305 

CHAPTER SEVEN 
Geometrical Constructions 319 



CHAPTER I 

PERSPECTIVE SKETCHING 

Prospectus 

It is the aim of this chapter to develop in a condensed but 
thorough manner the essential principles upon which perspective 
sketching is based. Furthermore, the presentation is intended to 
assist the student to develop a fair degree of skill in drawing 
perspectives of rectangular, angular, and cylindrical objects. 
Upon completion of the work of this chapter, he should be able 
to draw objects composed of a combination of these elementary- 
forms. It is hoped that the student will have gained confidence 
in his ability to visualize and represent an object pictorially. If 
this has been accomplished he will find a use for perspective as 
an interpretation of orthographic drawing which will be treated 
in the succeeding chapters. 




Fig. 1. Shaded Perspective of Try-Square 



General Principles 

A perspective drawing of an object shows it as it appears 
when viewed from a given position. Fig. 1 is an example of a 
perspective drawing. This drawing gives the observer a correct 
idea of the form and proportion of the object. 

9 



10 



MECHANICAL DRAWING 



The shading of the drawing, Fig. 1, while adding somewhat 
to its appearance, does not aid greatly in giving the correct 
impression of the form and proportion of the object. The shad- 
ing may, therefore, be omitted, leaving the simplest kind of 
drawing — the outline drawing as shown in Fig. 2. Such draw- 
ings will he referred to in this course as perspective sketches. 

Perspective sketches are valuable as a means of conveying 
information about the forms of objects to those who are not 
familiar with the more conventional means of representation 
used in mechanical drawing. The student will find the per- 
spective sketch an aid in interpreting mechanical drawing. 




Fig. 2. Perspective of Tey-Square 



In this course all objects to be drawn in perspective will be 
represented as resting on a horizontal plane directly in front of 
the observer and below the level of the eye. The try-square is 
shown in Fig. 2 as an observer would see it when standing 
directly in front of A B with his eye on the same level as S. 

In Fig. 2 the line marked horizon represents a line in space 
at an infinite distance in front of the observer. The eye of the 
observer is on a level with this line and is, consequently, above 
the level of the try-square, which rests on a horizontal plane. 

The horizon or horizon line is therefore an imaginary horizon- 
tal line on a level with the eye of the observer and at an infinite 
distance in front of him. The apparent meeting of sky and 
water when one looks over a large body of water is an example of 
a horizon. Since the horizon is always on a level with the eye 
of the observer, it follows that, as the eye is raised or lowered to 



PERSPECTIVE SKETCHING 11 

secure a different view of the object, the horizon will be raised 
or lowered the same distance. 

Direction of Lines in Perspective. Referring again to Fig. 2, 
we note that : 

1. In a perspective drawing all of the vertical edges of the 
object are represented by vertical lines in the perspective. 
Example : Lines A B and C D. 

2. In a perspective drawing all of the horizontal edges of the 
object which are at right angles with the direction of sight of the 
observer are represented by horizontal lines in the perspective. 
Example: While not an edge of the object, the horizon line. 
Fig. 2, is an example of this case. 

3. In a perspective drawing all of the horizontal edges which 
are parallel to each other, but not at right angles to the direction 
of sight of the observer, are represented by lines which converge 
to a point on the horizon. Example : Lines A C and B D. 

4. Horizontal lines receding to right and left in a perspective, 
which make equal angles with the horizon line, meet the horizon 
line at points equally distant from the point on the line directly 
in front of the observer. Example : In Fig. 2, S is a point on 
the horizon line directly in front of the observer. The distance 
from S to Vr is equal to the distance from S to Vl. 

45° Perspective. The angle between the beam and blade of 
the try-square is 90°. The try-square is so placed that the angles 
which the receding edges to the right and to the left make with 
the horizon are equal and must therefore be 45° angles. Because 
of this fact the try-square is said to be drawn in 45° perspective. 

All of the rectangular objects drawn in this course will be 
placed in a similar position to that of the try-square, i.e., in 45° 
perspective. This will insure comparative ease in the construc- 
tion of perspective sketches, as will, appear later. 

The points Vl and Vr on the horizon toward which the hori- 
zontal receding edges of the try- square converge are called 
vanishing points. 

A vanishing point is the common intersection of two or more 
converging lines which represent parallel receding edges of an 
object. 

All parallel horizontal receding lines must converge to the 



12 MECHANICAL DRAWING 

same point on the horizon. Example : The horizontal lines of 
the try-square converging to the right in its perspective meet in 
Vr. Likewise all the horizontal lines converging to the left meet 
in Vl. 

Vertical Lengths in Perspective. 

1. Equal distances on the same vertical edge of an object are 
represented by equal lengths in perspective. Example : In Fig. 
2 the try-square blade is represented as entering the beam mid- 
way between the upper and lower surfaces. The distance from 
A to the blade is equal to the distance from B to the blade. 

2. Equal distances on vertical edges of an object which are at 
unequal distances from the observer are represented by unequal 
lengths in perspective. Example : A B and C D represent equal 
lengths on the object but are unequal in the perspective. 

3. Of two equal vertical distances on an object the one nearest 
the observer is represented by the greater length in perspective. 
Example : A B and C D which represent equal vertical lengths 
on the object are both included between two lines of the drawing 
which converge toward Vr. On account of the convergence of the 
two receding lines C D is shorter than A B. 

Horizontal Lengths in Perspective. 

1. Equal distances on a horizontal receding edge of an object 
are represented by unequal lengths in perspective. Example : 
The spaces between the lines representing the one-inch marks on 
the try-square blade, Pig. 2, are unequal. 

2. Of the equal distances on a horizontal receding edge of an 
object, those farthest from the observer are represented by 
shorter lengths. Example : In Fig. 2 the spaces between the lines 
representing the one-inch marks grow shorter as they are farther 
away from the observer. 

3 Equal distances on a horizontal receding edge of an object 
are represented by lengths which appear equal. Example : The 
spaces between the lines representing the one-inch marks on the 
try-square blade. Fig. 2, are made to appear equal. 



PERSPECTIVE SKETCHING 13 

The varying of the lengths of lines representing equal 
distances on the object as described above is known as fore- 
shortening. 

Foreshortening is the process of shortening parts of a perspec- 
tive of an object so as to give the impression of true form and 
proportion. 

The Cube in Perspective. Thus far only a general considera- 
tion of perspective has been given. The following is an applica- 
tion of the principles thus far developed to the representation of 
a one-inch cube. 

In this course the cube will be regarded as the hasic form for 
all perspective drawing. The one-inch cube will be used as the 
unit of measure and therefore it is essential that its proportions 
and position with reference to the eye be well in mind. In Fig. 3 
the eye of the observer is directly in front of the point S. The 
vertical faces of the cube make 45° with the horizon and, also, 
with the direction in which the observer is looking. This agrees 
with the position of the try-square in Fig. 2 and is said to be in 
45° perspective as defined on page 11. In 45° perspective the 
distances from the point on the horizon directly above the nearest 
point of the object to the vanishing points and to the eye must 
be equal. In this course the vanishing points are taken 14" to 
the right and left of the point above the nearest corner of the 
object. 

The edges of the cube are one inch long. The front vertical 
edge of the cube will be the longest line in the perspective of the 
cube (See 3 under Vertical Lengths in Perspective). It will be 
drawn in its true length, one inch. 

The principles already developed are applied in the follow- 
ing analysis of the perspective of the cube. 

Since the side faces are equally inclined to the direction in 
which the observer is looking : 

1. Angle D A E = angle D'A E' 

2. Angle F B H = angle F'B H'. 

Such angles will hereafter be referred to as the angles of 
inclination. 



14 



MECHANICAL DRAWING 



The perspective of the corner G is directly above A. 

Due to the convergence of A D with B F and A D' with B F' : 

Angles F B H and F'B H' are greater than angles DAE 
and D'A E'. 



tpVl 



toVl 




toVr 




toVr 



Fig. 3. Perspective of One-Inch Cube 

Lines D F and D'F' are shorter than A B. D F = D'F'. Due 
to the convergence of A D with D'G and A D' with D G : 

1. G D and G D' are shorter than A D and A D' ; 

2. G C is shorter than C A. 



Due to foreshortening: 

A D and A D' are shorter than A B, 



PERSPECTIVE SKETCHING 



15 



Rectangular Objects 



PREPARATORY INSTRUCTION FOR DRAWING PLATE 1 

The following is a list of the materials needed to make the 
perspective sketches : 

1. Drawing board. 

2, High-grade drawing paper similar to Universal — 

9''xl2'' sheets. 

i3H 



3. High-grade pencils 



^5H 



4. Pencil pointer. 

5. Erasers — Ruby and Flexible gray. 

6. Thumb tacks. 

7. A straightedge — ruler or triangle. 







1 3 








C 




:: 


& 
u 

I 

ll. 
;o 

Id 

•a 

Q 

u 




y^ BORDER line: ^ 




o 




;: 




4 2 





Fig. 4. Position of Sheet on Drawing Board 



The drawing 'board should be made of well-seasoned, straight- 
grained, soft wood, free from knots and cracks. 

When in use the drawing board should be placed on the desk 
with the longer edges parallel to the front edge of the drawing 
table. It may be tilted to any convenient angle. 

Drawing Paper. In selecting a drawing paper the draftsman 
should have in mind the purpose for which it is to be used. For 



16 



MECHANICAL DRAWING 



freehand drawing, where it is desired to produce a porous, uni- 
form line with a soft pencil, a slightly grained surface is satis- 
factory. It should stand erasing without injury. 

In preparing to make a drawing, a sheet of paper should be 
tacked near the upper left hand corner of the board with the 
longer edges parallel to the longer edges of the board. Fig. 4. 
To fasten the sheet insert a tack in the upper left hand corner ; 










_^ 






li ■ - >> 

•1 \l 
< 1 >t 






'J 








1 



CORRECT AVOID 

Fig. 5. Position of Thumb Tacks 



square the paper with the board, and, stretching it diagonally, 
insert a tack in the lower right hand corner. Insert a tack in the 
upper right hand corner, stretch the sheet in the direction of the 
lower left hand corner, and insert a fourth tack. Press each tack 
down vertically until the head is firmly in contact with the paper. 
Fig. 5. 

Pencils. The lead of the drawing pencil should be of firm, 
even grain. To secure the .desired effect in the drawing, the 
hardness of the pencil must be considered in connection with the 
surface of the paper. For freehand drawing a medium soft 
pencil should be used on a slightly grained surface. A soft pencil 



PERSPECTIVE SKETCHING 



17 



is more easily controlled, and consequently there is more freedom 
in drawing lines with it than can be secured with a hard pencil. 
To sharpen the pencil, grasp it in the left hand as illustrated 
in Fig. 6, and with the knife in the right hand, cut the shavings 
by drawing the knife toward the body and through the wood 




Fig 6. Sharpening the Pencil. Whittling Away the Wood 




Fig 7. Sharpening the Pencil. Pointing the Lead 



only. About one-quarter inch of lead should be exposed, and the 
wood tapered back about one inch from the lead. Sharpen the 
lead on the surface of a sandpaper pad or file, rotating the pencil 
so as to produce a conical point. Fig. 7. The sharpened lead 
should be slightly rounded on the end in order that soft lines as 
shown in Fig. 8 may be produced. This figure also shows the 
sketching pencil properly sharpened. 



18 



MECHANICAL DRAWING 



The Constructive Stage. In making a freehand sketch all of 
the straight lines will first be drawn very lightly with the aid of 
a straightedge such as the edge of a triangle or ruler, using 
the 5H pencil. Fig. 12. 

1. When two points on a line are known the edge of the tri- 
angle or ruler should be placed so that its edge passes through 
both points. The line may then be ruled lightly. 

2. Sometimes only one point on the line and its general direc- 
tion will be known. In this case the edge of the rule should be 
made to pass through the point with the edge adjusted to the 
proper direction. 





1 

INCH 


^- 1 INCH 






[ i 


FINISHING line; 






MEDIUM PENCIL 








k 


CONSTRUCTION LINE 







HARD PENCIL 

Pig. 8. Sketching Pencil Properly Sharpened 



Ruling a Line. In ruling a line along a straightedge the 
pencil is held in the hand as indicated in Fig. 13. The line is 
drawn with a continuous motion from left to right with the tip 
of the fourth finger touching the ruler to steady the hand. The 
forearm should always he at right angles with the line teing 
drawn. The rule should preferahly he hetween the draftsman 
and the line being drawn. 

The Finishing Stage. When the constructive stage has been 
completed all lines which will not appear in the finished drawing 
should be erased. The 3H pencil should then be properly sharp- 
ened and the lines of the drawing traced over freehand. They 
must be uniform in width and grayness of tone. 

The Position of the Hand and Pencil in Sketching. In draw- 
ing a freehand line the pencil is held firmly, but not rigidly, 
between the first two fingers and the thumb as in writing. 

In six-etching a horizontal line the ends of the third and fourth 
fingers should rest upon the board to help support and steady 



PERSPECTIVE SKETCHING 



19 



the hand. Fig. 9. With the forearm resting on the drawing 
board, the hand should be moved from left to right, hinging at 




Fig. 9. Sketching a Horizontal Line 

the wrist. This will permit only short strokes, about one inch 
long, to be taken. To sketch a long line, therefore, one must 
join together a series of one-inch lines. The position for each 




Fig. 10. Sketching a Vertical Line 

stroke should be obtained by moving the hand and forearm in the 
direction of the line. Each section should be joined to the pre- 
ceding one, but not lapped upon it, as the lapping of sections 
produces an undesirable sketchy effect. 



20 MECHANICAL DRAWING 

In sketching a vertical line the hand is placed in the position 
shown in Fig. 10. The hand rests upon its side instead of upon 
the ends of the third and fourth fingers. The pencil is moved 
downward. The strokes are made with a finger movement while 
the hand remains stationary. In sketching a vertical line the 
forearm should remain approximately in the position of a vertical 
line on the sheet. 

The Border Rectangle. Before starting the drawing of the 
object on the sheet, draw a border line approximately one-half 
inch from each edge of the sheet. This may be done in the con- 
structive stage by placing the straightedge parallel to each edge 
of the sheet at a distance estimated to be one-half inch in from 
the edge, and ruling a line lightly. This border rectangle should 
be traced over freehand in the finishing stage as are the lines of 
the sketch. 

DATA FOE DRAWING PLATE 1 

Given: The perspective of a cube, Fig. 11. 
Required: To make a perspective sketch similar to that 
shown in Fig. 11, on a 9'' x 12" sheet as explained below. 

Instructions: 

1. Draw lightly the border rectangle y from the edge of 
the sheet. 

2. To locate the perspective of the cube use the 5H pencil with 
the ruler as a straightedge. 

a. Draw two very light horizontal lines XVr and YZ 

dividing the space between the upper and lower bor- 
der lines into three equal parts. 

b. Draw a vertical line, VW, through the center of the 

sheet and SU midway between VW and the left 
border line. 

c. From B estimate one inch up on S IT, thus locating A, 

the upper front corner of the cube. 

3. Vr is about ^'^ from the right border line. 

4. Draw lightly a horizontal line through A and connect A 
with Vr. 



PERSPECTIVE SKETCHING 



21 



5. Get the direction of A D' by drawing the angle of inclina- 
tion D'A E' equal to angle DAE. This may be accomplished by 
placing the ruler so that the edge passes through point A and 
adjusting its direction until the angles appear equal. Fig. 12. 

6. To obtain the Mddth of a vertical face of the cube, draw 
D F so that the figure A D F B appears as a square. Fig. 13 
shows the process of locating D F. A ruler or triangle is placed 




Fig 11. Perspective of Cube 

with an edge in a vertical position parallel to the line AB. It is 
then moved back and forth to right and left until, in the judg- 
ment of the draftsman, the figure A D F B appears as a square. 

7. Draw D'F' making AE'=AE. Complete the perspective 
of the cube by drawing D'Vr and D G. Fig. 11. 

This completes the constnictive stage. 

8. All lines not shown in Fig. 11 should now be erased. The 
cube and the border rectangle should be traced over freehand 
with a well sharpened 3H pencil to produce a line of even weight 
and uniform shade. The remaining lines of the drawing should 



22 



MECHANICAL DRAWING 



be allowed to remain light, as drawn in the constructive stage. 
Omit all reference letters. 

9. Write the plate number and name in the lower right hand 
corner of the sheet as in Fig. 11. Remove the sheet from the 
board, turn it over and, with a knife or other sharp instrument, 
press the paper back into the thumb tack holes. 

The Method of Developing Lettering in the Course. One of 
the most difficult steps in making a drawing is the lettering of 
the notes, dimensions, and title. In this course lettering will be 
omitted from all drawings until the student has had considerable 
practice in forming and spacing the letters and figures. This 
practice will be had on small lettering plates. Each drawing 
plate should he followed hy the lettering plate of the same 
number. 




Fig. 12. Sketching the Angles op Inclination 



Lettering 



Modern practice demands that the lettering done on working 
drawings be simple, legible, and capable of easy and rapid ren- 
dition. The simple Gothic style fulfils these requirements and 
is therefore quite generally used. 

Form and Proportion. A careful study of the form and 
proportion of each letter must be made before the student can 
hope to make any considerable progress in lettering. Practice 



PERSPECTIVE SKETCHING 23 

in drawing the letters will add something to his control of the 
media with which he works, but first of all he must have a dis- 
tinct knowledge of what he is trying to accomplish. 

Strokes. For convenience in- forming letters they are divided 
into strokes. In most cases the strokes are natural divisions of 
the outline of the letter. Three things should be remembered 
about the strokes for each letter: (1) the number of strokes, 
(2) the order in which they are made, (3) the direction in which 
each stroke is drawn. The advantage in knowing and using a 
system of strokes lies in the fact that drawing the letters repeat- 
edly in the same manner makes the forming of each letter more 




Fig. 13. Determining the Width of the Face of the Cube 

nearly automatic. Hence it adds to the ease with which letters 
can be produced and aids in securing uniform results. 

Spacing. Second only in importance to the forms of the let- 
ters is their relation to each other. The best effect is obtained 
when the areas included between the letters in a word appear 
equal. For the capital letters the area of these spaces should 
be equal to the area of a rectangle one-half the normal width 
of the H. The space between words should be about three times 
that between letters. Words set off by a comma should be spaced 
from one to one and one-half times the usual distance. The space 
between sentences should be about twice the space between words. 

The final test of good spacing is legibility. The letters must 
be far enough apart to avoid a crowded effect and yet the spaces 
must not be so great that the letters appear scattered. In like 



24 MECHANICAL DRAWING 

manner words must be separated enough to stand out individ- 
ually, but not enough to make reading difficult. 

Lettering in Pencil. The pencil used for the freehand work 
on a drawing should be softer than the pencil used for the 
mechanical work. It should be of such grade that when prop- 
erly sharpened a clear gray line can be produced with a single 
stroke. It should not be hard enough to cut into the surface of 




Fig. 14. Correct Position of the Hand and Pen for Lettering 

the paper, as difficulty is then experienced in controlling the 
direction of the line. 

The lead should be sharpened to a long taper, conical in 
form and rather blunt at the end. With one-quarter inch of 
lead exposed, and this tapered back to the wood, the section 
of the lead will be so nearly uniform near the end that it will 
stand considerable use without resharpening. The pencil should 
be held in the hand in the same position as the pen shown in 
Fig. 14, with the foreann nearly in the direction of the vertical 
stems of letters or, in the case of the inclined letters, nearly in 
the direction of the slant. The strokes should be drawn with a 
finger movement. The pencil should be turned about its axis 



PERSPECTIVE SKETCHING 25 

frequently to keep the point round so as to prodrce a line of 
uniform weight. All strokes should be made with the hand held 
in the same position Shifting the arm to obtain advantageous 
positions for drawing strokes in different directions is a habit 
which will prevent the acquirement of commercial speed and at 
the same time will prevent the development of the professional 
type of lettering as distinct from the labored effect produced by 
the average novice. 

Lettering in Ink. The beginner will find it more difficult to 
produce satisfactory results with pen and ink than with the 
pencil because of the complications which arise from the nature 
of the media. To secure a black line of uniform weight with a 
quick drying fluid such as India ink, and with an ordinary 
writing pen, presents a problem which usually requires a careful 
study of the methods of using these materials and considerable 
intelligent practice. 

The pen should be held in the hand as shown in Fig. 14. 
In drawing a line the points of the pen should be side by side 
so that the width of the line can be controlled by the pressure 
applied to spread the nibs. The position of the pen in the hand 
should not be changed for strokes of different direction, but 
rather the weight of line should be kept uniform by varying the 
pressure on the pen. In lettering in ink as in lettering with the 
pencil, the hand should be held in the same position for all 
strokes. This will give a better general effect and will make it 
easier to develop commercial speed in forming the letters. 

The pen should be filled by applying the quill attached to the 
stopper of the ink bottle to the under side of the pen. Enough 
ink should be put on the pen to last a reasonable length of time 
and to produce a wet line so that when it is dry, enough carbon 
will have been deposited to make it black. Overloading the pen, 
on the other hand, will cause the corners to fill at intersecting 
lines. The pen should be wiped frequently to remove the dry 
ink from the surfaces of the pen and between the nibs. Fresh 
ink and a clean pen are necessary to produce sharp clean-cut 
lines. 

Titles. The title contains information by which the drawing 
can be identified, such as the name of the part or parts of the 



26 



MECHANICAL DRAWING 



machine or structure, name of the complete machine or structure, 
manufacturer's firm name and address, drawing number, date, 
scale, and initials of draftsman, tracer, and checker. 

The usual position of the title is in the lower right-hand 
comer of the sheet where it does not interfere with the drawing 
and at the same time may be read without taking the sheet from 
its place in a drawer or file. The relative importance of the 
items in the title is shown by varying heights and widths of the 
letters or the weight of their stems, or both. 

The lines should be balanced, i.e., the middle point of each 
line should fall on the same vertical line. To give the best effect 



Q/vwiuoL dxAdnt/ d=^U: ^jJpoAhnmJj 



Ukrf/ DAAnAicnv 



Fig. 15. Title Material Divided into Groups of Words 



the lines should vary in length. The general contour of the title 
is very commonly oval or pyramidal in form. 

The arrangement of the lines of the title and the determina- 
tion of the height of each line present a problem in design for 
the solution of which the contour of the title should be kept in 
mind. 

The space between the lines of letters for the single stroke 
capitals should be from three-fourths to one and three-fourths 
the height of the smallest adjacent letters. 

The style of letter used for the title should be dignified. For 
this reason the capital letters are generally used. 

The steps in designing a title should be taken in about the 
following order: 

1. Assuming that the wording or at least the substance of 
the title is stated, write out the complete title and divide the 
words into logical groups for the different lines. Fig. 15. 



3^ 



PERSPECTIVE SKETCHING 27 

2. Eewrite, tentatively arranging the lines as they will be 
in the printed title. Fig. 16. 

3. Decide upon the relative importance of the lines and select 
heights of letters accordingly. It may now appear that a re- 
arrangement of the lines will give a better outline without affect- 
ing the meaning. 

Om/muxl dxmlnt ii 
E^^OAtrrumi/ a| TTLo/nuai/ (Mis/ 

WJlAmMJtwuWM^(mMm/ i" 

Fig. 16. Tentative Akeaxgement of Lines of the Title 

4. The title may be balanced by printing each line lightly in 
its proper space to obtain the spacing of the letters. Any 
adjustment necessary to make the middle point of each line fall 
on the center line of the title should be made. The letters should 
then be drawn in full weight. This method may be used with 

ANNUAL EXHIBIT 

WEST DIVISION HIGH SCHOOL 
DEPARTMENT OF MANUAL ARTS 

MILWAUKEE WISCONSIN 

Fig. 17. Finished Title 

success by those who have had considerable experience in letter- 
ing. The beginner will obtain better results with but little more 
work by lettering the lines first on a trial sheet to get the spacing 
and then by using these lines as a guide in balancing the lines 
and spacing the letters on the drawing, as described on page 140. 
Fig. 17 shows a balanced title. 

In drafting offices or business firms where large numbers of 
drawings similar in general character are made, the items com- 



28 



MECHANICAL DRAWING 



mon to all titles are very often printed on the pencil drawing 
with a rubber stamp and on the tracing in type. Uniformity in 
treatment is thus secured and much time in lettering is saved. 
Fig. 144 illustrates commercial titles. These title forms are 
printed on the under side of the tracing cloth. Errors may thus 
be corrected and changes made in the lettering done by the 
draftsman without erasing the printed lines and letters. 



EDGE OF CARD^ _ | 



BORDER LINE 



-ICO 



V 



-l!fi ioi£ 






K 



"^-T 



J_ 



Fig. 18. Lettering Card 



PEEPARATORY INSTRUCTIONS FOR LETTERING PLATE 1 

TJie Plate. The first ten lettering plates will be in pencil. 
Three by five cards of the regular drawing paper, ruled as shown 
in Fig. 18, will be used. 

The Lettering Pencil. Use the 3H pencil for lettering, sharp- 
ened to a conical point as for freehand sketching. Fig. 8. 

Number, Order, and Direction of Strokes. Each letter or 
numeral is made by one or more strokes. In general, vertical 
and inclined strokes are made downward and horizontal strokes 



PERSPECTIVE SKETCHING 



29 



to the right. Fig. 19 shows the number, order, and direction 
of strokes for the numerals 1, 4, 7, and the symbols used for 
the foot, inch, and dash. The relative width of numerals is 
shown in column 4. 




Fig. 19. Order, Number, and Direction of Strokes 

The Scale of Heights. For convenience in estimating ver- 
tical distances the space between the guide lines is divided into 
four equal parts. Fig, 19. 

A Scale of Widths. The width of the H is taken as the unit 
of width. The total letter distance is divided into four equal 
parts. Horizontal distances may be estimated by observing 
their relation to these divisions, Fiff. 19. 



30 MECHANICAL DRAWING 

Drawing the Strokes. Before starting a stroke, carefully 
plan its position and direction. Make each line with one move- 
ment of the pencil. A vertical stroke is made by drawing a 
line from one point to another directly 'below it. In case a stroke 
or letter is unsatisfactory it should be erased and redrawn. 

Foot and Inch Marks. A short dash placed to the upper 
right of a numeral indicates feet. Two such dashes similarly 
placed indicate inches. A horizontal dash is placed between 
numerals representing feet and inches. See Fig. 19. 




Fig. 20. LETTEPaxG Plate 1. 1, 4, 7 
DATA FOR LETTERING PLATE 1 

Given: Plate 1 to reduced size, Fig. 20. 
Required: To make the plate to an enlarged scale. 

Instructions: 

1. Fasten the card to the board either with thumb tacks or 
by inserting its comers in diagonal slits cut in a larger piece 
of paper which is tacked to the board. Fig. 18. 

2. Draw the numerals and symbols, using the number, order, 
and direction of strokes shown in Fig. 19. 

3. Write in the plate number, followed by the name at the 
top of the sheet as indicated in Fig. 20. 



PERSPECTIVE SKETCHING 



31 



PEEPARATORY INSTRUCTIONS FOR DRAWING PLATE 2 

Plate 1, page 21, gave practice iii making a perspective of 
the unit of measure and basic form in perspective — the cube. 
The one-inch cube will be used in the following plates as a 
means of constructing and proportioning the perspective sketches 
of more complex objects. 

A Scale of Levels. Fig, 21 shows a horizontal square at dif- 
ferent levels in perspective. At the left in Fig. 22 the horizontal 
square is used as the top of a cube, represented at levels one-half 
inch apart. It will be noticed that in each of these figures the 




Fig. 21. Vafjation op Area with Level 



area of the figure representing the square and the angle of 
inclination increase with the distance below the level of the eye. 
The distance below the level of the eye of the front corner of 
each square, Fig. 22, is indicated by the numerals at the left of 
the figure. In this course the student will be aided in determin- 
ing the level for the perspective of an object by referring to this 
scale. To the right of the scale is shown its application in repre- 
senting a cube at different levels. 

Vertical Measurements. Under, ''Vertical Lengths in Per- 
spective," page 12, the general facts regarding these measure- 
ments are given. In making vertical measurements in per- 
spective the following rule must be observed. 

All vertical distances on an object must be measured in per- 
spective on the line representing the front vertical edge of the 
object. This is true for the following reasons : 



32 



MECHANICAL DRAWING 



1. The front vertical edge is drawn full length. In Fig. 23, 
A B is greater than the vertical line through I. To secure this 
length, one would determine A B and draw tlie vanishing lines. 



HORIZON 




4i-' 



Fig. 22. Scale of Levels 



2. In general, equal vertical distances are equal in perspective 
only when measured on the same vertical edge. Example : 
AB = BK = KL. 



PERSPECTIVE SKETCHING 



33 




34 



MECHANICAL DRAWING 



Horizontal Measurements. Under, "Horizontal Lengths in 
Perspective," page 12, the general facts regarding horizontal 
measurements are given. In making horizontal measurements in 
perspective the following method should be used: 

Whenever possible, horizontal distances on an object should 
be measured in perspective by drawing the faces of a series of 
receding one-inch cubes so that they appear to be squares. In 
Fig. 23, lengths A D, D E, E G, G H, and H 1, representing equal 
horizontal distances, are measured by making faces 1, 2, 3, 4, and 
5 appear as squares. 




Fig. 24. Enclosing Solid 



The Enclosing Solid. In using the methods of making hori- 
zontal and vertical measurements given above, one of the impor- 
tant steps in the construction of the perspective sketch will be 
the drawing of a rectilinear solid the edges and surfaces of which, 
so far as possible, are coincident with the edges and surfaces of 
the object. Fig. 24. This solid will be called the enclosing solid. 
This solid should be drawn completely before any attempt is 
made to construct the details of the object in perspective. 

The Pleasure Cube. The first step in drawing the enclosing 
solid is to draw a one-inch cube with its upper front corner at 
the level required for the perspective of the object to be drawn. 
This one-inch cube will be at the upper front corner of the enclos- 



PERSPECTIVE SKETCHING 35 

ing solid. The front vertical edge of the cube serves as the ver- 
tical unit of measure and the width of the side faces as the hori- 
zontal unit of measure. This cube is therefore called the measure 
cube. 

The Table Line. When an object rests on a horizontal sur- 
face its position with reference to that surface is shown by a 
horizontal line called the table line. The position of this line as 
shown in Fig. 27 is taken arbitrarily. In its relation to the 
perspective it should represent the object as resting in a pleasing 
position on a horizontal plane. The table line should be drawn 
freehand. 

DATA FOR DRAWING PLATE 2 

Given: The dimensioned perspective of a sandpaper block, 
Fig. 27. 

Required: To make a sketch of the sandpaper block, full 
size in perspective, omitting all dimensions and lettering, or any 
similar problem assigned by the instructor. 

Instructions: 

1. Draw the border rectangle as in Plate 1, page 21. Here 
and throughout the constructive stage use the 5H pencil. 

2. To locate the center of the sheet proceed as follows : Place 
the ruler on the sheet with one edge in the position of one of the 
diagonals of the border rectangle. Rule a light, short line 
through the approximate center of the sheet. In like manner 
draw a part of the other diagonal. The intersecting lines will 
locate the center of the sheet. 

3. With the aid of the ruler draw the measure cube with its 
upper front corner A at the center of the sheet and 3^" below 
the level of the eye. Fig. 25. Refer to the angle of inclination 
in Fig. 22 for the required level. Reproduce this angle as 
illustrated in Fig. 12. 

4. Complete the enclosing solid by drawing the lines in the 
order indicated by the numerals. Fig. 25. Measure vertically 
and to the right and left as previously described under, ' ' Vertical 
Measurements" and, "Horizontal Measurements" respectively, 
pages 31 and 34. 



36 



MECHANICAL DRAWING 



5. To sketch the open space through the sandpaper block 
which is to be occupied when the block is in use by a block of the 




Fig. 25. Constructive Stage. Enclosing Solid 

same dimensions as the open space which holds the edges of the 
sandpaper, locate B, y.^' below A, and draw line 10 converging 




Fig. 26. Constructive Stage. Complete 

with line 3, Fig. 26. Lay off from A on line 3 a distance repre- 
senting y^' ' The principle of foreshortening applied here will 
make this distance slightly greater than one-half of the width 



PERSPECTIVE SKETCHING 



37 



of the face of the cube. Draw line 11. lu the same manner lo- 
cate and draw line 12. Draw lines 13, 14, and 15 converging 
with lines 2 and 6. Draw line 16 vertically from the intersection 
of lines 7 and 13. Draw line 17 converging with lines 3 and 7. 
This completes the constructive stage. 

6. Erase all lines except the outline of the figure and trace 
over the sketch freehand with a carefully sharpened 3H pencil. 
Draw a table line as in Fig. 27. 




Fig. 27. Sand Paper Block 

7. Write the plate number and name in the lower right hand 
corner of the sheet and press the paper back into the thumb tack 
holes as directed in Plate 1, page 21. 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 2 

Curved Strokes. In making the curved strokes of the 5 and 
the 2 the student should have in mind the form of the complete 
oval. 

The Dimension Form. The dimension form consists of the 
numerals designating feet and inches, the foot and inch marks, 
the dash, the dimension and extension lines, and the arrowheads 
as arranged in Fig. 77. 

It will be seen that the arrowheads are placed on the dimen- 
sion lines with their points touching the extension lines. They 



38 



MECHANICAL DRAWING 



are composed of two slightly curved lines symmetrical with 
respect to the dimension line. The length of the arrowhead 
should be about i'' and the width iV"- Fig. 77. Fig. 28 shows 
strokes for arrowheads pointing in different directions. 



STROKES 




:Y/. 



-AV 



3: 



WIDTH 


■""i r\"" 


Uli "■ 

..J 1 1 '■ 




...JJjTT- 



Fig. 28. Lettering Plate 
DATA FOE LETTERING PLATE 2 



Given: Plate 2 to reduced size, Fig. 29. 
Required: To make the plate to an enlarged scale. 
Instructions: Proceed as in Plate 1, page 30, following care- 
fully the number, order, and direction of strokes. 



PERSPECTIVE SKETCHING 



39 



DATA FOR EXTEA DRAWING PLATE 

Given: A dimensioned perspective sketch of a clamping 
plate for lathe tail-stock. 



5 5 5 5 5 1475 545 75457f 
2 22 22 425 5272 27527z 

liilliiiii TTTTTTTTTT- 



H 



Z |- 122'- 5"- 



V — 475'-2"— J 



2"- 



Fig. 29. Lettering Plate 2 



Required: To make a sketch of the clamping plate full 
size, omitting all dimensions. 




Fig. 30. Clamp for Tail Stock 



The upper front corner of the enclosing solid is in the center 
of the sheet and 3^" below the level of the eye. 



40 



MECHANICAL DRAWING 



Angular Objects 
PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 3 

To Center a Perspective Sketch on a Sheet. For the pre- 
ceding plates definite instructions have been given to center the 
sketch on the sheet. For the sake of appearance a sketch should 
be centrally located. The student should use considerable care, 
therefore, in locating the upper front corner of the enclosing 
solid. It cannot always be located at the center of the sheet. 
The following suggestions will be of value in locating the upper 
front corner of the enclosing solid. 

A close approximation can be made to the correct position of 
the front vertical edge of the enclosing solid to right or left of 
the center of the sheet by referring to Fig. 23. 




Fig. 31. Enclosing Solid 



1. On this figure the distance to be measured to the right and 
to the left of the front vertical edge of the enclosing solid may 
be marked off. If the horizontal distance between the extreme 
points is divided into two equal parts the division will come at 
the point in the perspective which should be at the center of the 
sheet. 

2. The distance from A B, Fig. 32, to this middle point is the 
distance which the front vertical edge of the enclosing solid 
must be to the right or left of the center of the sheet. 

In locating the upper front corner of the measure cube after 
the position of the front edge is determined, the length of the 
front edge of the enclosing solid and the distance of the back 
corner of the upper surface above the front comer of the enclos- 



PERSPECTIVE SKETCHING 



41 



ing solid must be estimated. Half the sum of these two distances 
should fall above and half below the center of the sheet. 

DATA FOE DRAWING PLATE 3 

Given: The dimensioned perspective sketch of a cord-wind 
with the upper surface 3" below the level of the eye. Fig. 33. 

Required: One of the two solutions as stated below. 

1. To draw the cord-wind, full size, with the upper surfaces 
5" below the level of the eye. Omit all dimensions and letters 
from the finished sketch. 




Fig. 32. Constructive Stage Complete 

2. To draw the cord-wdnd full size with the upper surface 5" 
below the level of the eye, and turned so that the longer edges 
vanish toward the left instead of toward the right. 

3. To draw any similar object assigned by the instructor. 




Fig. 



Cord-Wind 



Instructions: 

1. Locate the upper front corner of the measure cube A a3 
directed under, "To Center a Perspective Sketch on a Sheet," 
page 40. 



42 



MECHANICAL DRAWING 



2. Complete the enclosing solid as in Plate 2, page 35, taking 
care to secure the necessary convergence. As it is the aim that 
the student should learn to make perspective sketches entirely 
freehand he should now draw as many as possible of the lines of 
the constructive stage without the use of a straightedge. 

3. To locate the lines representing the cut in the near end 
of the cord-wind lay off A F and D E, Fig. 32, to represent one 




Fig. 34. Lettering Plate 



inch and H F and E I to represent one-half inch. From H and I 
draw lines converging with A N and D M to the right. Lay off 
A K to represent two inches and draw a line from K converging 
with A D. This line meets the lines from H and I in L and 
respectively. Connect E and F L. From draw a vertical 
line and from P a line converging with K 0. These lines inter- 
sect ni Q. Draw R Q. 

By a similar method make the construction for the cut at the 
farther end of the cord wind. 

4. Erase unnecessary lines and finish the sketch in the usual 
manner. 



PERSPECTIVE SKETCHING 43 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 3 

Curved Strokes. The oval of the numeral is the basic form 
for the 6 and 9. In making the outline strokes of these numerals 
the student should have in mind the form of the complete oval. 

Whole Numbers and Fractions. The whole number in a 
dimension will be made ^" high. 

The total height of the fraction should be twice the height 
of the whole number with a clear space between each numeral 
and the division line. Fig. 141. To check these heights mark 
off an eighth inch and a quarter inch space on the edge of a card 
and use it as a scale. Fig. 78. 



104 520 500 214: 
6 6 6 6 6 460 506 672 276: 
9 9 9 9 9 690 269 795 926: 

•4 ? 64 16 64 16 ^2 ^16 '^2 ^^16 16" 

.7" ^^. ^1" . ,o' r^^ 



■14-10;^ H 62-92 -^ — 16-0^- 



FiG. 35. Lettering Plate 3. 0, 6, 9 



DATA FOR LETTERING PLATE 3 

Given: Plate 3 to reduced size. Fig. 85. 
Required: To make the plate to an enlarged scale. 



44 



MECHANICAL DRAWING 



DATA FOR EXTRA DRAWING PLATE 

Given: The dimensioned sketch of a wall bracket, Fig. 36, 
with the upper surface of the enclosing solid 3^'' below the level 
of the eye. 

Required: To draw the wall bracket full size, with the 
surface as shown 3^'' below the level of the eye, but with the 
longer horizontal edges receding toward the left instead of toward 
the right. 




Fig. 36. Wall Bracket 



Cylindrical Objects 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 4 

The Veriical Measure Cylinder. As stated before, the cube 
is the basic form for the perspective sketching in this course. To 
secure a measure unit for cylindrical objects a cylinder is in- 
scribed in a measure cube as shown in Fig. 37. The cylinder is 
therefore one inch in diameter and one inch long. The principle 



PERSPECTIVE SKETCHING 



45 



of foreshortening makes the axis of the cylinder and the major 
axis of each of the ellipses representing its bases slightly less 
than one inch. In sketching, these differences may be ignored. 
In Fig. 38 these distances are one inch in length. 

The following is an analysis of a cylinder which will be 
referred to as the vertical measure cylinder: 

1. The distance between the centers of the ellipses is equal 
to their major axes or one inch. AB = CC' = DD'. Fig. 38. 

2. The major axes C C and D D' of the ellipses are at right 
angles with the axis of the cylinder. These lines do not eon- 





FiG. 37. Vertical Cylinder, In- 
scribed IN A Measure Cube 




Fig. 38. Vertical Measure 
Cylinder 



verge, since they represent lines at right angles to the direction 
of sight of the observer. See, "Direction of Lines in Perspec- 
tive," page 11. 

3. The minor axes E E' and F F' are coincident with the line 
representing the axis of the cylinder. 

4. Due to the difference in level of the upper and lower bases 
the minor axis F F' of the lower base is greater than the minor 
axis E E' of the upper base. The minor axis of the upper base 
may be determined for any level from the scale of levels discussed 
in the following paragraph. 

The half length of the minor axis of the lower ellipse may be 
determined by drawing F H' through D', converging with E H. 

A Scale of Levels. The left half of Fig. 39 is a scale of levels 
showing the upper base of a measure cylinder at levels one-half 



46 



MECHANICAL DRAWING 



inch apart. It is evident that the area and minor axis of the 
ellipse increase with the distance of the ellipse below the level of 
the eye. The distance below the level of the eye of the center of 



HORIZON 



fc: 





Fig. 39. Scale of Levels 



each circle, Fig. 39, is indicated by the numerals at the left of the 
figure. In this course the student will be aided in determining 
the level for the perspective of a cylindrical object by referring 



PERSPECTIVE SKETCHING 



47 



to this scale. To the right of the scale is shown its application in 
representing a cylinder at different levels. 

To Draw and Test an Ellipse Representing a One-Inch Circle. 

1. Draw light indefinite lines at right angles to each other to 
represent the axes of the ellipse. 









B 




T 


A 





^3 


. 









J 











Fig. 40. Testing an Ellipse 

2. On the line representing the major axis lay off on either 
side of the intersection of the axes one-half the diameter of the 
circle. 

3. Refer to the scale of levels ; estimate and lay off the minor 
axis. 

4. Sketch the ellipse lightly and freely, drawing correspond- 
ing parts in consecutive order, i.e., draw the long sides of the 




Fig. 41. Concentric Circles in Perspective 



ellipse and then the ends. Compare the form thus secured with 
the corresponding ellipse in the scale of levels. Care should be 
taken to avoid sharp or blunt ends. 

5. Ordinary defects in the form of the ellipse should be de- 
tected by examining it as follows : 

a. Turn the sheet to the right, to the left, and upside 
down, and view the form carefully when the sheet is in 
each of these positions. 



48 MECHANICAL DRAWING 

b. Locate two points as A and B, Fig. 40, on the axis 
equidistant from 0. The vertical distances from these 
points to the ellipse should be equal. Compare these dis- 




FiQ. 42. Split Core Bos — Axis Vertical 

tances and make the necessary corrections. Likewise lo- 
cate C and D equidistant from and compare the vertical 
distances from these points to the ellipse. Make the nec- 
essary corrections as before. 



Concentric Circles in Perspective 



The problem of drawing two concentric ellipses is more diffi- 
cult than that of drawing a single ellipse. 



PERSPECTIVE SKETCHING 49 

Fig. 41 shows two concentric ellipses inscribed in concentric 
squares shown in perspective. The ellipses therefore represent 
circles. On account of foreshortening, the axes of the ellipses do 
not coincide with the line representing the diameter of the circles 
or with each other. In most cases the difference is so slight that 
it may be ignored. For very large ellipses, however, the construc- 
tion shown in Fig. 41, where the major axis of the larger ellipse is 




Fig. 43. Split Core Bos — Axis Horizontal 



slightly in front of the major axis of the smaller ellipse, must 
be used. 

In Figs. 42 and 43 the major axis C F is laid off equal to the 
diameter of the circle, as in the case of the ellipse representing 
a one-inch circle. Fig. 38. A one-inch ellipse should be drawn 
first and tested. In cases where the major axes of the ellipses are 
made to coincide, the half length of the minor axis of a larger or 
smaller ellipse may be determined as shown in Figs. 42 and 43. 
C D is drawn through C parallel to A B. In cases where the axes 
do not coincide the line corresponding to C D should be made to 
converge slightly with A B. 



50 



MECHANICAL DRAWING 

DATA FOR DRAWING PLATE 4 



Given: The dimensions of a split core box for standard 
one-inch cores, which consists of a hollow cylinder split into 
halves ; outside diameter 2", inside diameter 1", length 3". 

Required: A perspective sketch of the split core box with 
its axis vertical and the upper base 3" below the level of the eye, 
Fig. 42, or any similar object assigned by the instructor. 




Fig, 4-i. Lettering Plate 4 

Instructions : 

1. Draw through the center of the sheet a vertical line to 
represent the axis of the cylinder. All lines should now be draw7i 
freehand. 

2. Through points 1^"* above and below the center of the sheet 
draw horizontal lines as the major axes of the ellipses represent- 
ing the ends of the bushing. The minor axes will coincide wIlIi 
the axis of the cylinder. Care should be taken to make the angle 
between these axes a right angle. 

3. Draw the ellipse representing the smaller circle in the 
upper end of the core box at the required level. Refer to the 
scale of levels to estimate the major and minor axes of the ellipse. 
Draw the ellipse with these axes and test it as described under, 
"To Draw and Test an Ellipse," page 47, 

4. Lay off the major axis and determine the length of the 
minor axis of the larger ellipse as described under, "Concentric 
Circles in Perspective," page 48. 



PERSPECTIVE SKETCHING 



51 



5. Only one-half of the larger ellipse representing the lower 
end of the bushing will be seen. The length of the minor axis 
of this ellipse may be found by the method illustrated in Fig. 42. 
H G is drawn through G converging with E F. While only the 
lower half of the ellipse will be needed, the complete ellipse should 
be drawn as construction. 

6. Complete the constructive stage of the sketch by drawing 
the vertical contour elements of the cylinder which join the ends 
of the major axes of the large ellipses. 

7. Erase all construction lines and complete the sketch in the 
usual manner. 





_Qia^4- JoAn/Bcz^^ 


z8 8 8 8 8 418 698 785 829 z 


z3 3 3 3 3 136 983 568 3921 z 


Z 1^36-8"— ^ 1— 23'-9|— >| 

_ ^^8-10 >\ Y '^'-32 n 00 CO 


oo — 
D — 


Z 1— l3'-2^'— H |^I69'-0|'^ _ 




— 


1 



Fig. 45. Lettering Plate 4. 8, 3 

PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 4 

The combination of ovals in the 8 serves as a basic form for 
the 3. In making the curved strokes of these numerals the stu- 
dent should have in mind the form of the complete oval. 



DATA FOR LETTERING PLATE 4 

Given: Plate 4 to reduced size. Fig. 45. 
Required: To make the plate to an enlarged scale. 



52 



MECHANICAL DRAWING 



DATA FOR EXTRA DRAWING PLATE 

Given: The dimensions of a picture frame as shown in 
Fig. 46. 

Required: To draw the picture frame as though it were 
lying on a table, with its upper surface 4'' below the level of the 
eye. At this level a portion of the bottom of the hole will be 
visible. 







h- 


4 DIAM. 

s'diam. 


'-i 


i 


^ 


#r-i5 


t 


<S^>cf 


-i- ""7K A 






[ 





Fig. 46. Picture Frame Section 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 5 

The Horizontal Measure Cylinder, Fig. 47 shows a horizontal 
cylinder inscribed in a measure cube. This cylinder is therefore 
one inch in diameter and one inch long. Due to foreshortening, 




Fig. 47. Horizontal Cylinder In- 
scribed IN A Measure Cube 



Fig. 48. 



Horizontal Measure 
Cylinder 



the major axis of the nearer base is slightly less than one inch, 
and the axis of the cylinder is shorter than the line representing 
the horizontal edge of the measure cube. 

These differences are so slight that they will be disregarded 
in the following analysis of the cylinder, which will hereafter be 
referred to as the horizontal measiire cylinder. Fig. 48. 



PERSPECTIVE SKETCHING 



53 



Figs. 49 and 50 are similar to Figs. 47 and 48, respectively, 
but show a horizontal cylinder at a different level, with its axis 
receding to the right instead of to the left. 

1. Since the axis of a horizontal cylinder in 45° perspective 
always extends toward a vanishing point, the inclination of the 
axis indicates the level at which the cylinder is drawn. Figs. 48 
and 50. 

2. The major axis of the bases are perpendicular to and the 
minor axis coincident ivith, the axis of the cylinder as in the 
vertical measure cvlinder. 




Fig. 49. Horizontal Cylinder 
Inscribed in a Measure Cube 



Fig. 50. 



Horizontal Measure 
Cylinder 



3. The major axis of the nearer base is equal in length to the 
diameter of the cylinder, or one inch. The major axis of the far- 
ther base is shorter, on account of the convergence of the contour 
elements of the cylinder. 

4. The distance between the centers of the bases is equal to 
the horizontal receding edge of the measure cube, which is ap- 
proximately three-fourths of the front vertical edge of the cube. 
Since the major axis of the near base is drawn equal to the front 
vertical edge of the measure cube, or one inch, the distance 
between the centers of the bases may be taken as three-fourths 
the length of the major axis of the near base. This ratio remains 
constant for all ordinary levels. 

5. It will be noticed in Figs. 48 and 50 that the minor axes 
of the nearer bases are practically equal to the distance between 
the centers of the bases or three-fourths of the major. axis of the 



54 MECHANICAL DRAWING 

nearer base. When the nearer ellipse is drawn, the half length 
of the minor axis of the farther ellipse may be determined by 
drawing a line CD through D, converging with AB. Fig. 48. 
These lines do not converge toward a point on the horizon line, 

DATA FOR DRAWING PLATE 5 

Given : The Split Core Box represented in Plate 4. Fig. 43. 

Required: To draw the Core Box in a horizontal position 
with its axis 4^" below the level of the eye, or any similar object 
assigned by the instructor. 

Instructions: 

1. Draw through the center of the sheet a line in the direction 
of one of the vanishing points, to represent the axis of the cyl- 
inder at the required level. The angle of inclination may be 
obtained from Fig. 22. 

2. Refer to Fig. 23, estimate, and lay off three foreshortened 
inches on the axis. One-half of this length should fall on either 
side of the center of the sheet to locate the drawing centrally on 
the sheet. 

3. Draw through the points thus determined the major axes 
of the bases at right angles to the axis of the cylinder. 

4. Draw the ellipse representing the nearer end of the Core 
Box as shown in Fig. 43. C F is made equal in length to the 
outside diameter of the Core Box, 2". D is determined by draw- 
ing C D through C parallel to AB. Test each ellipse as described 
under, "To Draw and Test an Ellipse," page 47. 

5. From the ends of the major axis of the larger ellipse draw 
contour elements converging with the axis of the cylinder to 
determine the ends of the major axis of the farther base. 

6. The half length of the minor axis of the farther base may 
be determined as shown in Fig. 43. HG is drawn through G 
converging with E F. E F and H G do not converge toward a 
point on the horizon line. While only one-half of the farther 
ellipse will show in the finished drawing, a better result will be 
obtained by drawing the complete ellipse as construction. 

7. Erase all construction lines, including the axes of the 
ellipses, and finish the sketch in the usual manner. 



PERSPECTIVE SKETCHING 



55, 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 5 

Horizontal and Vertical Strokes. As stated under Plate 1 
vertical strokes are usually made downward and horizontal 
strokes to the right. 



HIT 



Fig. 51. Spacing op Adjacent Vertical Stems 

The direction of horizontal and vertical strokes must be exact. 
The relative width of the letters is shown in column 4. Fig. 52. 



STROKES 


1 


2 


3 








1 












1 






— .... 






i 








hn 

HIM 


1 


1 



WIDTH 








III 












III 
1 1 




■ riT 




— 


illli 



Fig. 52. Lettering Plate 



Spacing. In this and the following plates practice in mak- 
ing individual letters will be followed by practice in making 



56 MECHANICAL DRAWING 

words. In order that the lettering may present a good appear- 
ance, it is as important that the letters be well spaced as that 
they be properly formed. 

Correct spacing depends more on the judgment of the drafts- 
man than on any rule which might be given. However, it may 
be said that as a rule the letters should appear to be equally 
spaced. 




Fig. 53. Lettering Plate 5. I, L, T, H 

For this style of letters adjacent vertical strokes should be 
a distance apart equal to one-half the width of the H. Example : 
H and I, Fig. 51. Letters of irregular form should be placed 
at such a distance that the space appears equal to that between 
the H and I. Example : I and T, Fig. 51. 

When spacing a letter the beginning of the first stroke should 
be carefully located. 

DATA FOR LETTERING PLATE 5 

Given: Plate 5 to reduced size. Fig. 53. 
Required : To make the plate to an enlarged scale. 



PERSPECTIVE SKETCHING 

DATA FOR EXTRA DRAWING PLATE 



57 



Given: The dimension of a picture frame as shown in 
Fig. 46. 

Required: To draw the picture frame as though it were 
hanging flat against a vertical wall, with its center 3" below the 
level of the eye. 

Extension op Perspective Theory 

PREPARATORY INSTRUCTIONS FOR EXTRA DRAWING PLATES 

The Measure Cube in New Positions. In the preceding plates 
the measure cube was drawn at different levels, but always with 
its side faces at 45° with the horizon. 




Fig. 54. Drawing a Cube at Any Angle 

If the measure cube is turned with its side faces making other 
angles with the horizon, the number of positions in which an 
object may be drawn will be increased. 

Fig. 54 shows a method of constructing a measure cube at 
any level and with its side faces at any desired angle. The steps 
in the construction are as follows : 

1. Draw an ellipse representing a two-inch circle at the 
required level. 



58 



MECHANICAL DKAWING 



2. Draw a semi-circle of the same diameter as the circle 
represented by the ellipse, with its center at the center of the 
ellipse. 

3. Mark off on the semi-circle the angles which the faces of 
the cube are to make with the horizon. These angles should be 
90° apart. 

4. Vertical lines through these points intercept the ellipse 
in the ends of the nearer edges of the upper face of the cube. 
These edges meet at the center of the ellipse which is the upper 
front corner of the cube. 




Fig. 55. 



Cylinder Inscribed in a 
Measure Cube 



Fig. 56. Measure Cyi.indkr. 



5. Make the front vertical edge one inch long as in 45° 
perspective. 

6. Complete the cube by drawing the remaining edges con- 
verging so as to give the faces of the cube the appearance of 
squares. It will be noted that the farther edges of the upper face 
intersect on the line making 45° with each of the side faces. 

The Measure Cylinder in New Positions. Fig. 55 shows a 
horizontal cylinder inscribed in a measure cube with its side 
faces at other than 45° to the horizon. This cylinder is there- 
fore one inch in diameter and one inch long. Due to foreshort- 
ening, the major axis of the nearer base is slightly less than one 
inch and the axis of the cylinder is shorter than the line rep- 
resenting the horizontal edge of the measure cube. These differ- 
ences are so slight that they will be disregarded in the following 
analysis of the measure cylinder. Fig. 56. 



PERSPECTIVE SKETCHING 



59 



1. The distance between the centers of the bases is equal to 
the horizontal receding edge of the measure cube. This distance 
will be shorter as the angle of the axis of the cylinder to the 
horizon increases. 

2. The major axes of the bases are perpendicular to, and the 
minor axis coincident with, the axis of the cylinder. 

3. The major axis of the nearer base is equal in length to 
the diameter of the cylinder, or one inch. The major axis of 
the farther base is shorter on account of the convergence of the 
contour elements of the cylinder. 




Fig. 



57. Cylinder Inscribed in a 
Measure Cube 



Fig. 58. Measure Cylinder 



4. The length of the minor axis of the nearer base will depend 
upon the angle that the axis of the cylinder makes with the 
horizon. Fig. 56 illustrates the case in which the minor axis is 
lengthened, due to the axis of the cylinder making an angle 
greater than 45° with the horizon. Fig. 58 illustrates the case 
in which the minor axis is shortened, due to the axis of the cylin- 
der making an angle less than 45° with the horizon. The length 
of the minor axis for other positions may be estimated by using 
Figs. 56 and 58 as guides. For any angle the axis of the cylinder 
makes with the horizon the length of the minor axis will remain 
the same for all levels. When the nearer ellipse is drawn, the 
half length of the minor axis of the farther base may be deter- 
mined by drawing a line C D through. D, converging with A B. 
Figs. 56 and 58. 



60 



MECHANICAL DRAWING 



DATA FOR EXTRA DRAWING PLATE 
Given: The objects shown in Figs. 59, 60, 61, and 62. 




Fig. 59. Concrete Block 



Required: To draw one or more of the above objects in 
positions selected from the following table by the instructor. 




Fig. 60. Nail Box 



The level at which the object is drawn may be assumed by the 
student. 



PERSPECTIVE SKETCHING 



61 



The right vertical face of tlie enclosing solid makes one of 
the following angles with the horizon : 



1. 15°. 



2. 30^ 



3. 60^ 



4. 11 



The objects should be centered on the sheet as in previous 
problems. 




Fig. 61. Broom Holder 



Review Questions 

1. (a) What is the horizon? (b) How is it represented? 
(c) What is its relation to the eye? 

2. (a) What is a vanishing point? (b) Where is it located? 

3. Where do parallel horizontal lines appear to meet in per- 
spective ? 

4. Do vertical lines appear to converge in perspective? 

5. (a) What is meant by foreshortening? (b) Are the per- 
spectives of equal lengths on the same vertical edge equal? 
(c) On the same horizontal edge? (d) Are the perspectives of 
equal vertical lengths at different distances from the observer 
equal ? 

6. (a) What is the angle of inclination? (b) How does it 
vary? 



62 



MECHANICAL DRAWING 



7. (a) In what position on the drawing board is the paper 
fastened? (b) How is it fastened? 

8. Describe in detail how the pencil should be sharpened for 
sketching. 

9. (a) What is the position of the hand and pencil in sketch- 
ing horizontal lines? (b) Vertical lines? (c) What is the 




Pig. 62, Bird House (Dimensioned Perspective) 



essential difference? (d) What movements are made to produce 
the line ? 

10. (a) What is meant by constructive stage? (b) Finish- 
ing stage ? 

11 In what way does a scale of levels assist in making a 
perspective of a rectangular object ? 

12. (a) Where are all vertical measurements laid off in per- 
spective? (b) Why? 



PERSPECTIVE SKETCHING 

13. How are horizontal measurements made ? 

14. Explain what is meant by enclosing solid. 



6S 




Fig. 63. Book Eack (Dimensioned Perspective) 

15. (a) What is a measure cube? (b) Why is it called a 
measure cube ? 




Fig. 64. Form for Testing Concrete Prisms 

16. Of what use is the table line ? 

17. (a) How do you proceed to locate the drawing centrally 
on the sheet? 



64 MECHANICAL DRAWING 

18. How are the perspectives of the inclined lines located? 




Fig. G6. Pen Eack 



19. (a) Give the proportions of the vertical measure cylinder, 
(b) The major axes of the bases are at what angle with the axis 
of the cylinder? 



PEESPECTIVE SKETCHING 65 

20. How does the difference in level affect the appearance of 
a horizontal circle in perspective? 

21. Of what assistance is a scale of levels in drawing a vertical 
cylinder ? 

22. How is the ratio of the minor axes of two ellipses repre- 
senting concentric circles determined ? 

23. (a) Give the proportions of a horizontal measure cylin- 
der, (b) The major axes of the bases are at what angle with the 
axis of the cylinder? (e) What is the relative length of the 
major and minor axes of the nearer base ? 

DATA FOR REVIEW DRAWING PROBLEMS 

Given: The objects shown in Figs. 63, 64, 65, 66. 

Required: To draw one or more of the above objects in 45* 
perspective. The level at which the object is drawn may be 
assumed by the student. 



CHAPTER II 

ORTHOGRAPHIC SKETCHING 

Prospectus 

In this chapter the work of the preceding chapter will be 
continued in order that the value of the perspective sketch as an 
aid in interpreting orthographic views may be apparent. At the 
same time more general application will be made of perspective 
principles and additional skill acquired in representing objects 
pictorially. 

It is the chief aim of this chapter to familiarize the student 
with the method of representation generally used in working 
drawings. By the time the work of this chapter is finished the 
student should be able to read drawings of ordinary complexity 
as well as to make freehand orthographic sketches with a con- 
siderable degree of skill and confidence. 

PREPARATOEY INSTRUCTION FOR DRAWING PLATE 6 

Views. ^ In perspective sketching the object is viewed from 
one position, so chosen as to show its three general dimensions in 
one view. Such a means of representation does not show the prin- 
cipal surfaces of an object in their true form and proportion or 
the principal edges in their true lengths. 

In order to represent the principal surfaces of an object in 
their true form and proportion and the principal edges in their 
true length, the object is usually viewed in two or more direc- 
tions, viz. : from directly in front, directly above, or directly from 
the right or left. Each view thus secured will give the exact 
form and proportion of the surfaces and the true lengths of the 
edges toward which one is looking perpendicularly. Views thus 
secured are known as orthographic. In mechanical drawing 
orthographic views are generally used. 

66 



ORTHOGRAPHIC SKETCHING 67 

Pig, 69 shows two views of a bench stop. The view marked 
TOP represents orthographically what is seen from directly 
above the object and the view marked front represents what is 
seen from directly in front of the object. The top view shows 
two general dimensions in horizontal directions, viz. : the dimen- 
sion from left to right and the one from front to back. The front 




Fig. 67. Type Problem. Perspective of Bench Stop 

view shows the horizontal dimension from left to right and the 
vertical dimension. Thus the three general dimensions are given 
in the two views and the proportions of the object are determined. 
Relation of Top and Front Views. It should be clear from 
the above statement that one of the general dimensions, viz. : 
the horizontal dimension from left to right, is common to the 
front and the top views. For this reason as a matter of con- 
venience in making and interpreting the drawing it is essential 
that the top view always be placed directly above the front view. 



68 



MECHANICAL DRAWING 



Under this condition all distances from left to right may be 
projected from one view to the other. 

'^Beading" the Drawing. To form a mental image of an 
object the relation of its surfaces, edges, and comers as repre- 
sented must be studied. This process is called reading the draw- 
ing and is illustrated under the four following headings: (The 
present discussion is confined to rectangular solids.) 




Fig. 68. Type Problem. Constructive Stage of the Okthogkaphic 

Sketch 



Plane Surfaces. Fig. 69 represents an object having plane 
surfaces. 

1. When the observer is looking perpendicularly at a surface 
it appears in its true form and proportion. Example : The 
rectangular top surface A B C D of the bench stop, Fig. 69, is 
represented in its true form and proportion in the top view. 

2. When the observer is looking edgewise at a plane surface 
it appears as a straight line. Example : Line E F is the front 
view of the top surface A B C D. Fig. 69. 



ORTHOGRAPHIC SKETCHING^ 



69 



Straight Edges. 

1. A straight edge viewed at right angles to its length shows 
as a line in its true length. Examples The front edge of the 
top surface of the bench stop shows in its true length in line A B 
in the top view and in line E F in the front view. 

2. A straight edge viewed endwise appears as a point. Exam- 
ple : Point F is the front view of the edge B C. Fig. 69. 



J_ 



-JG 



-d-^ 



k' 



1^ B H SCREWS d 



'"2 
TOP 



,.. I FRONT 

4 



-tt 



p: 



:£: 






c^^jzz^^i^rf^ib^t. 



FiG. G9. Type Pkoelem. Finished Sketch of Bench Stop 



Curners. A corner appears as a point when viewed from any 
direction. Example : The upper front corners at the left of the 
bench stop are represented by A in the top view and E in the 
front view. 

Invisible Edges. Hidden edges or hidden surfaces viewed 
edgewise are represented by dotted lines to distinguish them from 
visible edges or surfaces. Example : 6 H in the top view. 
Fig. 69. 



70 



MECHANICAL DRAWING 



Problems and Questions on Orthographic Principles 

The student should test his knowledge of the orthographic 
principles just stated by answering the following questions : 
See Fig. 70. 

1. (a) Where is the front view of the horizontal surface 9, 
10,15,16? (b) Of 10, 12, 13, 15? (c) Of 9, 11, 14, 16? 

2. (a) Where is the top view of the horizontal surface 5, 4? 
(b) Of 8,1? 



2 



Fig. 70. Review Problem 



3. (a) Where is the top view of the front vertical surface 
1, 2, 3, 4, 5, 6, 7, 8? (b) Of the rear vertical surface 1, 2, 3, 
4,5,6,7,8? 

4. (a) Where is the top view of the vertical surface 7, 8? 
(b) Of 3, 4? (c) Of 5, 6? 

5. (a) Where is the top view of the front horizontal edge 
2,3? (b) Of 7, 6? 

6. (a) Where is the front view of the rear horizontal edge 
15,13? (b) Of 16, 14? 



ORTHOGRAPHIC SKETCHING 71 

7. (a) Where is the front view of the upper horizontal edge 
10, 15? (b) Of 12, 13? 

8. (a) Where is the top view of the edge 5? (b) Of 6? 

9. (a) Where is the front view of the upper front corner 12 ? 
(b) Of 9? (c) Of the upper back corner 15? 

10. (a) Where is the top view of the front corner 2? (b) 
Of 5? 

The Type Problem. In each of the following problems pre- 
sented for solution the methods to be employed and the results 
to be obtained will be illustrated by a type problem. This type 
problem will consist of two parts : 

1. A drawing of an object similar to, and represented in the 
same manner as, the one given for solution. 

2. A solution of the problem corresponding to that required 
of the student. 

Example: Fig. 69 is the type problem for the first ortho- 
graphic sketch. Fig. 67 is the perspective of the bench hook 
shown in Fig. 69 and corresponds to the kind of a drawing the 
student will make from Fig. 71, 72^ or 73. 

Materials. The materials used for the plates in this chapter 
are the same as those used in perspective sketching (see page 
15; except that in this case the 5H pencil will be used for both 
the constructive and finishing stages. 

Perspective STcetcTies. In this chapter perspective sketches 
will be drawn preceding the orthographic sketches as a means of 
interpreting the orthographic views and at the same time to 
continue the practice necessary to develop skill in representing 
objects in perspective. 

DATA FOR DRAWING PLATE 6 

Given: An orthographic sketch, Fig. 71, 72, or 73. 

Required: To draw a 45° perspective sketch of the object 
shown in Fig. 71, 72, or 73 as assigned by the instructor, with 
the upper front corner of the enclosing solid 3|'' below the level 
of the eye or any similar object assigned by the instructor. 



T~ 



jL_ 






'T7i~ 

I iniCD 



^AiC/. J^^Bc 



Fig. 71. Gain Joint 



- 


- 









-s — 3' 


— >j 




,— TIN BOX 








^^ 


__J ■ 


1 




--IM 1 








12" 




=1 -Jf-J 
■i' y 








>. 





-■c^ "tZ-^-JtrA-vty i£l> -d^ 



(72) 



Tig. 72. Scouring. Board 



ORTHOGRAPHIC SKETCHING 



73 



Instructions: 

Use the comer marked A as the upper front corner of the 
object. All lines of this drawing are to be made freehand, includ- 
ing the light lines in the constructive stage. Omit all dimensions. 




Pig. 73. Cement Fern Jar 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 6 

Inclined Strokes. Before starting an inclined stroke, the stu- 
dent should sense its direction, moving the pencil between its 
two ends without touching the paper. 



DATA FOR LETTERING PLATE 6 



Given: Plate 6 to reduced size. Fig. 75. 
Required: To make the plate to an enlarged scale. 



74 



MECHANICAL DRAWING 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 7 

The Constructive Stage. This stage in orthographic sketch- 
ing is similar to the constructive stage in Perspective Sketching 
described on page 18. It consists of drawing all lines of the 
sketch lightly and full. No attempt should be made to make 
the lines exactly the right length in this stage. When drawing 



STROKES 


1 


2 


3 


4 




_ 


zir- — 




I 










.=1^ ... 


i 


...L— ... 


...I 


i 


1 


^ 












1 


l^= 


M 


Vi 











WIDTH 


.... 


lilt" 




N 

ill "'"■ 



Fig. 74. Lettering Plate 



each line it should be made long enough to give all necessary 
intersections with other lines. 

By this time the student should have gained such facility in 
drawing freehand lines that he will not need the rule to draw 
straight lines. 

If a straightedge is used at all in this chapter it should be 
necessary only in ruling long lines in the constructive stage and 
in locating one view directly opposite another. 



ORTHOGRAPHIC SKETCHING 75 

In laying out the views of an orthographic sketch on the sheet, 
proceed in the following manner : 

1. Referring to Fig. 68, mark off tentatively the position of 
the extreme right and left of each view. Shift both marks to the 
right or left, if necessary, to make A equal B. 

2. In like manner mark off the vertical dimensions of each 
view, leaving a space between the two views proportional to that 
which is shown in the figure. This distance should be from f 



_QU^6 


fl^i^An/ Q/7^ _ 


=FFFFF 


LIFT FIFTH FIT IF f 


=EEEEE 


FILLET FILE TELL = 


zNNNNN 


FIN NINETEEN FIN f 


zMMMMM ELEMENT LIMIT = 


fpEElT TENTH MILE NINE LIME FILM |Z 



Fig. 75. Lettering Plate 6 

to 1". Shift all marks up or down if necessary to make C 
equal D. 

3. Make any necessary adjustments in the general propor- 
tions of the views. 

4. In proportioning the details of the views, a comparison of 
the dimensions of each detail with the dimensions of the views in 
which it appears will aid in securing good results. Example: 
In the front view, Fig. 69, the width of the cleats is about one- 
sixth of the total length of the bench hook and their thickness is 
twice that of the board to which they are fastened. 



76 



MECHANICAL DRAWING 



Finishing Stage. As in Perspective Sketching, the finishing 
stage consists in erasing unnecessary lines made in the construct- 
ive stage, tracing over the outline of the drawing, and otherwise 
giving it a finished appearance. The student should proceed as 
follows : 

1. Erase all construction lines and retrace the lines of the 
drawing, using a 5H pencil. 

2. Represent all invisible edges by dotted lines which are 
composed of i" dashes with ^j" spaces between them. The ends 
of the dashes should be made definite by placing the pencil on the 




Fig. 76. Dotted Lines 



paper, moving it the required length, and then removing it as 
nearly as possible vertically from the paper. Fig. 76 shows the 
correct method of joining dotted lines to full lines. 

3. Place the dimensions on the sketch as described below 
under, ''Arrangement of Dimensions." 

Arrangement of Dimensions. Dimensions are placed on a 
drawing as shown in Figs. 71 and 72 to show the size of the 
object represented Only those dimensions are given which are 
necessary to determine completely the size of the object. 

An over-all dimension is one which shows the distance from 
one extreme point to another. Example : The five inch dimen- 
sion in Fig. 71. A detail dimension is one which shows the dis- 
tance between two points on some part or detail of the object. 
Example : The three and one-half or one inch dimension. Fig. 73. 



ORTHOGRAPHIC SKETCHING 



77 



When detail dimensions and a dimension representing their 
sum are given, they should be grouped in parallel lines. The 
shorter dimension should be near the outline of the object to avoid 
the confusion arising from the crossing of lines. Example : Those 
below the front view, Fig. 69, are properly arranged. 

The Dimension Form. Fig. 77 shows what is known as the 
dimension form. It includes all of the elements of the convention 
used in indicating linear dimensions on a drawing. The following 
points should be noted : 




Fig. 77. Dimension Form 



1. Horizontal dimensions read from left to right. 

2. Vertical dimensions read from the bottom toward the top 
of the sheet. 

3. Extension lines begin about sV from the outline of the 
object and continue |'' beyond the arrowhead. 

4. The space between the outline of the object and the nearest 
dimension line or between two parallel consecutive dimension 
lines is about \". 

5. Arrowheads are placed on the dimension lines at their 
extreme ends. 

6. Arrowheads are composed of two slightly curved lines sym- 
metrical with respect to the dimension line. The length of the 
arrowhead should be about ^" and the width ■}^'\ Fig. 77. The 



78 MECHANICAL DRAWING 

strokes for arrowheads pointing in different directions are shown 
in Fig. 28. 

7. The whole number in the dimension figure will be made 

¥' high. 

8. The total height of the fraction in the dimension figure is 
twice that of the whole number with a clear space between each 
numeral and the division line. 



5^ 

^8 



Fig. 78. Showing Actual Heights of Whole Number and FuAdTioN 

To check these heights of numerals in a dimension figure, mark 
off an eighth-inch and a quarter-inch space on the edge of a card 
and use it as a scale. Fig. 78. 

9. The dimension figure is generally located centrally in the 
dimension line, which is broken sufficiently to admit it. 



DATA FOR DRAWING PLATE 7 

" Given: Orthographic sketches, Figs. 71, 72, and 73. 
Required: To make an orthographic sketch of the object 
shown in Fig. 71, 72, or 73 ; or any similar object as assigned by 
the instructor, on a 9"x 12'' sheet. 

Instructions: 

1. Draw a border line as in perspective sketching. 

2. The rectangles shown about the drawing in Figs. 71, 72, 
and 73 are proportional to the size of the 9''x 12" sheet and the 
border rectangle. The over-all lengths of the view of the sketch 



ORTHOGRAPHIC SKETCHING 



79 









" 


STROKES 




WIDTH 

Mil 
illli 

1 1 1 1 1 

Ik 

Hill 




1 


2 


3 




1 


= ' 


7 


IK 

S 




... ) 


1 




// 




/ 


\ 























Fig. 79. Lettering Plate 




Fig. 80. Letteri.\g Plate 7. K, Y, Z, A 



80 MECHANICAL DRAWING 

should bear the same ratio to the dimensions of the sheet as the 
corresponding dimensions in the figure bear to the size of the rec- 
tangle representing the sheet. With this in mind proportion the 
views and locate them centrally on the sheet as previously 
explained. 

3. Draw in the details and finish the drawing of the views, 
as usual. 

4. Draw in the extension lines, dimension lines, arrowheads, 
and numerals following the directions given under, "Arrange- 
ment of Dimensions," page 76. 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 7 

As stated under Plate 6, the student should sense the direc- 
tion of an inclined stroke before drawing it. 

The spacing between irregular letters should ap]>ear equal 
to the area of one-half the H. Fig. 81. 

KEY 

Fig, 81. Spacing of Irregular Forms 
DATA FOR LETTERING PLATE 7 

Given: Plate 7 to reduced size. Fig, 80. 
Required: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 8 

It is customary to draw the top and front views of an object 
when these views will show the form and proportions satisfac- 
torily and when only two views are needed. Some objects are of 
such a form, however, that a front view and a view from one 
side are needed to determine completely the form of the object. 
The particular side view is selected which will represent the 
object by the use of the least number of dotted lines. Fig. 82 
represents an object which would be well defined by the use 

% 



ORTHOGRAPHIC SKETCHING 



81 



of a front view and one side view. The right side view would 
be the one chosen in this case. Since the two side views contain 
the same information, if one is given the other may be drawn. 
As previously explained, an observer sees all vertical dimensions 
and the horizontal dimension from left to right in the front 
view. All vertical dimensions and the horizontal dimensions 
from front to back are seen in the side view. 

A right side view is always placed directly to the right and a 
left side view directly to the left of the front view. This is done 
both for the sake of convenience in making and reading a draw- 




fRONT 

Tig. 82. Beveler 



RI6HT sioe 



ing and because an observer, when viewing an object, would, 
after obtaining the front view, naturally step to the right for 
a right side view or to the left for a left side view. To secure 
the front view after the side view is drawn, or to secure the side 
view after the front is drawn, all vertical distances may be 
projected from the first of the two views drawn. Fig. 82 shows 
the front view and the two side views of an object in their 
proper relative positions. 

Inclined Surfaces. Any surface which is at right angles to 
the line of sight, when an object is being viewed, will show 
in its ti*ue form and size. A surface which makes other than a 
right angle with the line of sight is called an incliried surface. 
Such surfaces do not show in their true form and size. Fig. 82 
represents an object having inclined surfaces. If one surface is 



82 



MECHANICAL DRAWING 



rectangular and two of its edges are at right angles to the direc- 
tion in which it is inclined, as in the ease of the surface C D E F, 
Fig. 82, the vertical dimension of the rectangle representing the 
surface in the front view is less than the actual width of the 
surface. 

The inclined surface C D E F is represented by the inclined 
line G H in the left side view. G H is equal to the true width of 
the surface, G'H', representing the same surface in the right 
side view, is also equal to the true width of the surface. It must 
be evident from a study of Fig. 82 that in representing any rec- 
tangular inclined surface which has two of its edges at right 
angles to the line of sight, the dimension represented by these 




Fig. 83. Construction for Angles and Hidden Corners (Perspective) 



edges will show in its true length. C D and E F, perpendicular 
to the direction of sight in the front view, show the true length. 
of the rectangle in this view. 

The end edges, G H and G'H' of the surface C D E F, are 
perpendicular to the direction of sight in the side views and 
therefore show the true width of the surface in these views. 

Inclined Edges. A straight edge which is not at right angles 
to the direction in which it is viewed is represented by a line 
shorter than the actual length of the edge. Example : The end 
edges of the surface C D E F are represented in the front view, 
Fig. 82, by lines C E and D F. These lines are shorter than 
the actual lengths of the edges, as shown by lines GH and 
G'H' in the side views. 

In sketching an angle where the direction of the edge is given 
by dimensions locating two points on the edge, the line represent- 



ORTHOGRAPHIC SKETCHING 



83 



ing the edge should be determined by laying off the dimensions 
given to locate the points on the line. Where the dimension is 
given in degrees the ends of the inclined lines should be located 
by estimating the lengths of the legs of the right triangle of 
which the inclined line is the hypotenuse. Example : The length 
of the lines A B and A C, Fig. 83, are laid off to determine the 
direction of B C. For a 45° angle A B and A C represent equal 
distances. For a 60° angle AB is roughly -j^ of AC. 

In determining the position of a line passing through an 
invisible corner, such as E F, Fig. 83, make a construction for 
the invisible corner by drawing lines B E and E G. 

The student should test his knowledge of the orthographic 
principles just stated by answering the following questions: 




I a 3 4 



Fig. 84. Review Problem 



Problems and Questions in Orthographic Principles 
Refer to Fig. 84. 



1. Where is the side view of the inclined surface 1, 2, 7, 8? 

2. (a) Is line 1, 2 equal to the true width of the inclined 
surface? (b) Where is its true length shown? (c) Why? 

3. Where is the inclined edge 1, 8 shown in its true length? 
Why? 

4. (a) Is the vertical surface 11, 15 on the front or back of 
the object ? (b) Why ? (c) Where is it shown in the front view ? 

5. Where is the vertical surface 14, 13 shown in the front 
view ? 



84 



MECHANICAL DRAWING 



6, Where is the horizontal surface 13, 16 shown in the front 
view? 

7, Where is the horizontal surface 6, 7 shown in the side view ? 

8, Where is the vertical surface 4, 9 shown in the side view ? 





f 


'I-'- 










-^ — . 





RIGHT END 



(P/cCtD f.J,rlLu ».rt- 



Fig. 85. Type Problem. Hardie. Given Views 



DATA FOR DRAWING PLATE 8 



Given: Orthographic sketches, Figs. 88 and 89, 90 and 91. 

Required: To draw a 45° perspective sketch of the object 
shown in Fig. 88, 89, 90, or 91, or any similar object as assigned 
by the instructor. 

The upper front corner of the enclosing solid is 2^" below 
the level of the eye. Use the point marked A as the upper front 
corner of the measure cube. All lines of this sketch including 
the constructive stage should be made entirely freehand. Omit 
all dimensions. 




Fig. 86. Type Problem. Hardie. Perspective Sketch 




Fig. 87. Type Problem. Hardie. Required Views 







A A 
















-A A 


















t 














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/ 


J 


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/ 




\ 


/ 


j V 


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— 4"- — * 




^<- — 4- — 


— ^ 








— 6" 







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Fig. 88. Sheet Metal Hopper 




(86) 



Fig. 89. Knife and Fork Box 




Fig. 90. Bench 




Fig. 91. Book Eack 



STROKES 


1 


2 


3 


4 










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/ / 


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WIDTH 

iiiii 

M 

iiiiiii 

IIIM 

iiiii 

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Fig. 92. Lettering Plate 




Fig. 93. Lettering Plate 8. V, W, X, U, J 



ORTHOGRAPHIC SKETCHING 89 

DATA FOR LETTERING PLATE 8 

Given: Plate 8 to a reduced size. Fig. 93. 
Required: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 9 

Dimensioning Angles. The inclination of an edge or surface 
is commonly determined by giving dimensions which fix two 
points on the line, usually its ends. Example : The wedge end 
of the hardie. Fig. 85. In some cases it is desirable to give the 
inclination of an edge or surface in degrees. In this case the 
dimension line is an arc with its center at the intersection of the 
two lines forming the angle. Example : The 45° angle in the 
end of the bench. Fig. 90. 

Solution of the Problem. Attention is called to the fact that 
in the following problems the student is required to draw dif- 
ferent views from those given. Read the statement of the 
problem carefully before starting to draw. 

DATA FOR DRAWING PLATE 9 

Given: Orthographic sketches, Figs. 88, 89, 90, and 91, 
showing the front and left side of each of the objects. 

Required: To draw the front and right side views of the 
object shown in Fig. 88, 89, 90, or 91, or any similar object as 
assigned by the instructor. 

Instructions : 

1. Block in the views of the object as described on page 75 
and as carried out in Plate 7, so that they are in the center of the 
sheet. 

2. Complete the details of the views in light lines. 

3. Trace over the lines as explained on page 76, making them 
the proper weight. 

4. Draw in the dimension lines and put in the arrowheads 
and figures in the order given on page 77. 



90 



' MECHANICAL DRAWING 



5. Write in the plate number and name as usual. Press the 
paper back into the tack holes. 



Sb 



Fig. 94. Spacing of Curved Forms 



STROKES 



L 



[J 



2 3 



a 



n 



g: 



WIDTH 



n: 



Fig. 95. Lettering Plate 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 9 

The letter is wider than the numeral 0. 

The forms of the Q, C, and G are based on the oval of the 0. 



ORTHOGRAPHIC SKETCHING 91 

Spacing Curved Stroke Letters. As stated in the instruc- 
tions for Plate 5, the area included between the contour of two 
adjacent letters should appear equal to the area of one-half of 
the H, "When a vertical stroke and a curved stroke are properly- 
spaced the clear distance between them is slightly less than one- 
half the width of the H. Example : The I and 0. Fig. 94. 

The clear distance between two curved strokes will be less 
than that between vertical and curved strokes. Example : The 
and in Fig. 94. 



_(Mi^f 


^^r7d^^(r5^_ 


=00000 


ONYX AVIATION |z 


f QOOOO 


QUAIL ANTIQUITY z 


zCCCCC 


CHEQUE CONNECTION z 


zGGGGG 


ENGINE GAUGE r-5^"z 


zDDDDD 


LADLE HEAD FLOAT Z 



Fig. 96. Lettering Plate 9. 0, Q, C, G, D 

When spacing a letter having a curved outline the begin- 
ning of the first stroke should be carefully located. In planning 
the letter, the clear space between it and the previous letter should 
be held in mind. 

DATA FOR LETTERING PLATE 9 

Given: Plate 9 to reduced size. Fig. 96. 
Eequired: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 10 

Objects thus far sketched for which orthographic views were 
drawn have had plane surfaces. In Plate 10 an object having 
cylindrical surfaces is to be represented orthographically. 



92 



MECHANICAL DRAWING 



Cylindrical Surfaces. In Fig. 97 an object having cylin- 
drical surfaces is represented by orthographic views. 

1. The outline of the front view represents cylindrical sur- 
faces when viewed at right angles to their axes. 

2. A simple cylinder, when viewed in this direction, appears 
as a rectangle. 




( ,t<ij.i^ I! Q.ci-'-v^ Go 



Fig. 97. Type Problem. Given Views of a Shaft Coupling 

3. The straight lines representing the bases of the cylinder, 
A B and C D, Fig. 97, are equal in length to the diameter of the 
cylinder and represent the bases of the cylinder viewed edgewise. 

4. The straight lines representing the contour elements of the 
cylinder A C and B D are the elements of the cylinder which 
divide the visible part of the surface from that which is invisible. 
They are viewed at right angles to their direction and are there- 
fore shown in their true length. See page 81 under "Inclined 
Surfaces." 

As stated in discussing the representation of plane surfaces, 
a surface viewed edgewise is represented by a line. In the case 



ORTHOGRAPHIC SKETCHING 



93 



of a plane surface the line representing the surface is a straight 
line. 

When a cylindrical surface is viewed in the direction of its 
axis the observer is looking at the surface edgewise and it there- 
fore appears as a line, which in this case is a circle. Example : 
EFGH, Fig. 97. 




Fig. 98. Type Problem. Perspective of a Shaft Coupling 

Circular Edges. 

1. A circular edge viewed at right angles to its plane shows 
as a true circle. Example : E F G H in Fig. 97. 

2. A circular edge viewed in the direction of its plane shows 
as a straight line equal in length to the diameter of the circle. 
Example: A B and CD in Fig. 97. 

The student should test his knowledge of the orthographic 
principles just mentioned by answering the following questions : 
See Fig. 102. 

1. (a) Where is the left end view of the cylindrical surface 
3,4,11, 12? (b) Of 1, 2,13, 14? 



94 



MECHANICAL DRAWING 



2. Where is the front view of the cylindrical surface 25, 26, 
27, 28 ? 

3. (a) Where is the circular surface 1, 16, 15, 14, shown in 
the end view? (b) Where is the surface 2, 3, 12, 13 shown in 
the end view? 

4. (a) Where is the circular edge 6, 9 shown in the end view ? 
(b) Where is the circular edge 4, 11 shown in the end view? 

5. What surface would be crosshatched if a quarter section 
were made cutting on the lines 0, 17 and 0, 18 ? 

6. What surface would be crosshatched if a half section were 
made cutting on the line 17, 19 ? 

7. (a) Where is the left end view of the extreme element 
3, 4? (b) 11, 12? 




Pig 99. Half Section. Quarter Section. Illustrated in Perspective 



DATA FOR DRAWING PLATE 10 



Given: Orthographic sketches. Figs, 103 and 104. 

Eequired: To draw a perspective sketch of the object 
shown in Fig. 103, 104, or any similar object as assigned by the 
instructor, with its axis vertical. The upper end of the object is 
2-^'' below the level of the eye. 




Fig. 100. Type Problem. Constructive Stage of the Orthographic 

Sketch 




<f-/kxL II jH^^^^iyt, 



Fig. 101. Type Problem. Finished Sketch of a Shaft Coupling 

(95) 



96 



MECHANICAL DRAWING 




Fig. 102. Eeview Problem 




Fig. 103. Cylinder Head 



ORTHOGRAPHIC SKETCHING 



97 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 10 

The first two strokes of the P, R, and B are exactly alike. 
The basic form of the S is a combination of two ovals. When 
drawing the strokes of the S these ovals should be held in mind. 



1 r 

X 



JL_ 




O^ccZZ. // l-irh..^ k)f^ 



Fig. 104. Spring Casing 



DATA POR LETTERING PLATE 10 

Given: Plate 10 to a reduced size. Fig. 106. 
Required: To make the plate to an enlarged scale. 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 11 



Objects thus far drawn have been shown in their complete 
form. By referring to Fig. 97 it will be noticed that all hidden 
contour elements are represented by dotted lines. When there 



98 



MECHANICAL DRAWING 



are too many of such lines they tend to confuse the reader of the 
drawing. 

Half Section. If an object is represented as though a portion 
of it has been removed, the drawing can often be made much 
clearer because of the reduction in the number of dotted lines. 



STROKES 


1 


2 


3 




= - 


^ 




y- 


R 


1 


SEE 


c 




C 

. .V. 


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WIDTH 


.... 
.... 


B 
B 

III 

S 
& 

III 


^-. 



Fig 105. Lettering Plate 



A common method of showing a part removed is to imagine the 
object cut into two similar parts through an axis of symmetry. 
Fig. 99. 

The cut is made in a plane at right angles to the line of sight 
and the near half of the object is imagined removed. The 
observer then sees the cut surfaces of the remaining half in their 
true form and proportions. The view thus obtained is called a 
half section view. Example : See the front view. Fig. 101. 



ORTHOGRAPHIC SKETCHING 99 

It should be noticed that a part of the object is imagined re- 
moved only in the drawing of one view. The end view, Fig. 101, 
represents the complete object. 

Quarter Section, Another common method of representing 
an object is to imagine it cut on two planes at right angles to 
each other in to an axis of symmetry. Fig. 99. One of the cut 
surfaces is at right angles to the line of sight and the other is 
parallel to it. The quarter of the object included between the 




Fig. 106. Lettering Plate 10 

two cut surfaces is considered removed. The observer then sees 
the cut surfaces in one plane in their true form and proportions, 
and those in the other plane appear as a line. Fig. 101. The 
view thus obtained is called a quarter section. It should be 
noted here again that a part of the object is imagined removed 
only in the drawing of one view. 

Crosshatching. The cut surfaces in the section view are rep- 
resented conventionally by crosshatching, which consists of 
drawing very fine parallel lines, equally spaced, over a surface 
represented as cut. In the student problems the lines should be 
drawn about -jV'' apart and at an angle of 45° with the hori- 
zontal. Both the distance between the lines and the angle at 



100 MECHANICAL DRAWING . 

which they are drawn should be estimated — not measured. It is 
suggested, however, that after drawing the first few lines the 
student check the spacing with a scale. The angle of the cross- 
hatch lines should be carefully checked in a corner where hori- 
zontal and vertical boundary lines meet at right angles. Wlien 
the distances from the corner to each end of the same Crosshatch 
line are equal, the angle is 45°. 

Center Lines. A line which represents an axis of symmetry 
is called a center line. Center lines may be straight or curved. 
Of the straight lines there are two classes, principal and sec- 
ondary. A principal center line is one about which the entire 
view is symmetrical. Example : A C in Fig. 101. The principal 
center lines should extend about |" beyond the outline of the 
view. A secondary center line is one about which only part of 
the object is symmetrical. Example : E F, Fig. 101, is the center 
line for the hole only. Secondary center lines should extend 
about ;|'' beyond the outline of the part of which they represent 
the axes. 

A circular center line usually passes through the centers of a 
number of holes grouped at a certain distance from a central 
point. It is not quite a complete circle. Example : See left end 
view, Fig. 101. 

In general, every circle in a drawing must have two center 
lines at right angles with each other. Example : Lines 17, 19 and 
18, 20. Fig. 102. When one of the center lines is circular, as in 
the case of the center line for the drilled holes in the end view, 
Fig. 103, the other center line is at right angles to the tangent 
of the circular center line, it the center of the hole. This line 
is therefore a radial line from the center of the circular center 
line. 

Dimensioning Cylindrical Surfaces and Circles. The diam- 
eter of a cylinder may be given by placing the dimension on a 
diameter of the circle representing the cylindrical surface. 
Example : See Fig. 101. It may be given between extension lines 
drawn from the rectangular view. Example : See Fig. 101. In 
this case the dimension figures should be followed by a Z> or 
Diam. to indicate that the dimension is a diameter. A hole to 
be drilled, cored, or bored may be indicated by printing the word 



ORTHOGRAPHIC SKETCHING 101 

showing how it is to be obtained or finished, together with the 
dimension and arrow pointing to the hole. The word and the 
dimension should be placed in an open area near the hole rep- 
resented. The line drawn under the word should be about ^^" 
below the letters. Example : See Fig. 101. 

To Sketch a Circle. 

1. Through the center of the circle draw two light lines at 
right angles, and on each lay off points at a distance from the 
center equal to the radius of the circle. 

2. Repeat this process by drawing another pair of lines which 
make 45° with the first pair. In case the circle is large other 
similar lines may be drawn which bisect the angles made by the 
first lines. 

3. Sketch in the circle through the points located on the 
several lines. This should be done with great care. The first 
lines drawn should be very light. 

4. When the circle is complete observe its form carefully and 
true it up by erasing and redrawing any portion which is untrue. 

5. In the finishing stage the corrected light lines should be 
traced over to produce a line of the proper weight. 



DATA FOR DRAWING PLATE 11 

Given: Orthographic sketches, Figs. 103 and 104, or any 
similar problem selected by the instructor, showing the front and 
right end views. 

Required: To draw the front quarter sectior and left end 
views of the objects shown in Fig. 103, 104, or any similar ob- 
ject as assigned by the instructor. 

Instructions: 

1. Proportion the views on the plate. 

2. Draw the principal center lines for the circular view. 
Draw the circles in the following order: (1) The larger circles. 



102 MECHANICAL DRAWING 

(2) Circular center line. (3) The circles representing the small 
holes. 

3. To draw the rectangular view, first determine its vertical 
dimensions by projecting from the end view. Complete the view. 

4. Retrace the lines as in the finishing stage, giving particu- 
lar attention to those affected by the section. 

5. Draw in extension and dimension lines and put in the 
dimensions. Finish the sketch by crosshatching the cut surfaces. 
Care should be taken to make the section lines parallel to each 
other and at 45° to the horizontal. 



Lettering in Ink 

PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 11 

The following is a list of the materials used in making letter- 
ing plates in ink. 

1. Tracing Cloth, 4'' x 6" sheets. 

2. One of the following or any similar pen which will give 
satisfactory results may be used: 



303 Gillott's 
404 Gillott's 
Spencerian No. 1 
Lady Falcon 



•Three of each. 



3. Penholder. 

4. Black waterproof drawing ink. 

Square one of the three by five inch cards on the board and 
stretch the tracing cloth over it with the dull side up. The sur- 
face of the cloth should be prepared for inking by being rubbed 
with chalk dust. All superfluous ch^alk must be removed to 
prevent its clogging the pen. The guide lines for the letters 
should be drawn on the cloth in pencil. When the plate is 
finished a border rectangle should be drawn and the sheet 
trimmed to 3"x5". Fig. 18. The space outside the cutting 
lines may be used to try the pen on during the process of let- 
tering the plate. A pen should be selected which will give a 



ORTHOGRAPHIC SKETCHING 103 

width of line suited to the height of letters to be made. The 
proper width of line should be secured with but little spreading 
of the nibs of the pen. Fig. 14 illustrates the position of the pen 

ROUGH ROUND RODS 
OHIO CORLISS ENGINE 

Fig. 107. Examples of Word Spacing 

in the hand while lettering. Note that the forearm is nearly 
parallel to the vertical strokes. Vertical strokes should be made 
with a finger movement. In making the horizontal and curved 
strokes this movement is combined with a turn of the wrist. 



1 


_{2^// 


(^^c;A^^^{^^ _ 


z CLAMP 


TENSION WEIGHING FIXED Z 


Z FULL SIZE 


YOKE BLOCK LOCOMOTIVE Z 


Z VALVE MOTION SCALE FULL SIZE Z 


z ANGLE 


TENSION WEIGHING FIXTURE Z 


Z FULL SIZE 


CORE REAM PLATE GIRDERZ 


1 



Fig. 108. Lettering Plate 11 

To fill the pen, place the ink on the under side by means of 
the quill attached to the stopper of the bottle. The stopper 
should be returned to the bottle since the ink dries rapidly. 

Composition. In this and the following plates in lettering, 
words wiU be combined into phrases and sentences. The spacing 
of words plays an important part in securing a good general 



104 MECHANICAL DRAWING 

effect in a line of letters. The space between words should appear 
equal to three times that between letters or one and one-half 
times the width of the H. Adjacent vertical strokes will there- 
fore be separated by a space one and one-half times the width of 
the H. The clear distance between two words having vertical 
strokes adjacent to a curved stroke will be less than one and 
one-half times the width of the H. The clear distance between 
two words having adjacent curved strokes will be still less. 
Example : See Fig. 107. 

DATA f OE LETTERING PLATE 11 

Given: Plate 11 to reduced size. Fig. 108. 

Required : To make the plate to an enlarged scale. In this 
plate the wording of the titles for the first pencil mechanical 
drawing plates is used. The letters are approximately the height 
used in the title. 



Review Questions 

1. (a) In what direction does one look at an object in 
making its orthographic views? (b) How does this differ from 
the way it is viewed in making a perspective of it ? 

2. (a) How many general dimensions does each orthographic 
view show? (b) How many orthographic views are necessary to 
show three general dimensions? 

3. (a) What is the position of the top with reference to the 
front view? (b) Why? (c) Which general dimension is com- 
mon in the top and front views ? 

4. What is meant by "Reading" a drawing? 

5. (a) Under what condition does a surface appear as a line 
in a view? (b) When a hidden surface is viewed edgewise how 
is it represented? 

6. (a) When is a plane surface snown in its true form in one 
view and as a straight line in the other? (b) When is a plane 
surface shown in less than its true size in one view and as a 
straight line in the other? 



ORTHOGRAPHIC SKETCHING 105 

7. (a) When is a cylindrical surface represented as a rec- 
tangle? As a circle? (b) When is a circular surface repre- 
sented as a straight line in one view and as a circle in the other ? 

8. (a) When is a straight edge of an object shown in its true 
length in two views? (b) When in its true length in one view 
and as a point in the other? (c) When in its true length in one 
view and in less than its true length in the other? 

9. How are the corners of an object represented ? 

10. Describe the process of proportioning the views of an 
object and locating them centrally on the sheet. 

11. What are the lengths of dashes and spaces in dotted lines ? 

12. (a) Illustrate by a sketch how detail and over-all dimen- 
sions are grouped, (b) What space is allowed between the out- 
line of the object and the nearest dimension line? (c) Between 
dimension lines? 

13. (a) Where is the right side view placed with respect to 
the front view? (b) Where is the left side view placed with 
respect to the front view ? 

14. (a) What general dimensions of an object are shown in 
the right side view? (b) In the left side view? 

15. What determines the choice between a right and left side 
view? 

16. (a) Why is an object sometimes shown with a part re- 
moved? (b) Define quarter-section. Define half-section, (c) Is 
the part cut by the section planes shown as removed in both 
views ? 

17. (a) What is the purpose of crosshatching ? (b) At what 
angles are the crosshatching lines drawn ? (c) What is the usual 
distance between crosshatching lines? 

18. (a) What is a principal center line? (b) A secondary 
center line ? 

19. (a) When is a straight center line used? (b) Circular 
center line ? 

20. (a) How many center lines must be drawn for each 
circle? (b) At what angle to each other? 

21. Illustrate how the two views of a cylinder may be 
dimensioned. 






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— I 



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(106) 



Fig. 110. Vise Jaw 



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RIGHT SIDE 



Fig. 111. Turning Tool Holder 



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Fig. 112. Valve Bonnet 



(107) 



108 



MECHANICAL DRAWING 



DATA FOE REVIEW PROBLEMS 

Given: An orthographic sketch, Fig. 109. 

Required: To make the orthographic sketch shown in Fig. 
109 to an enlarged scale. 

Given: An orthographic sketch, Fig. 110, showing the front 
and left side views of the object. 

Required: To draw the front and right side views of the 
object shown in Fig. 110. 





^4- 


T" 






1 


lb 1 


1 *9" 





h 



■H — 



Fig. 112A. Dovetail Cross Slide 



Given: An orthographic sketch, Fig. Ill, showing the front 
and right side views of the object. 

Required: To draw the front and left side views of the 
object shown in Fig. 111. 

Given: An orthographic sketch, Fig. 112, showing the front 
and left side views of the object. 

Required : To draw the front quarter section and right side 
views of the object shown in Fig. 112. 



ORTHOGRAPIITC SKETCHING 109 

Given: Orthographic sketches, Fig. 112 A, showing the 
front and left side of each of the objects. 

Required: To draw the front and right side views of the 
object shown in Fig, 112A as assigned by the instructor. 



CHAPTER III 
PENCIL MECHANICAL DEAWING 

Prospectus 

In this chapter orthographic sketching is continued. A more 
general application of the principles of orthographic drawing is 
made. This is done principally by introducing problems requir- 
ing three views from perspective sketches. It is the chief aim 
of this chapter to give considerable practice with some of the 
common instruments and materials used in making mechanical 
drawings and to fix a standard of technique. "When the work of 
this chapter is completed, the student should be able to make 
neat, accurate mechanical drawings of simple objects. The tech- 
nique of the lettering, arrowheads, and figures should be of a 
standard comparable with that secured in the mechanical line 
work. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 12 

Three-view Problems. From the principles developed in 
Chapter II it is evident that each view shows two of the general 
dimensions of an object. and therefore only two views are neces- 
sary to obtain all three of the general dimensions of any object. 
However, in some cases all of the general dimensions, length, 
height, and thickness may be given and still the form of the ob- 
ject will not be clearly defined. When this is true a third view is 
necessary. A top, front, and side view are drawn with the top 
above the front view and the side view to the right or left of the 
front view as in the problems of Chapter II. 

Example : The front and side views of the part of a Sash 
Joint in Fig. 113A do not show the form of the tenon. Hence 
a top view is necessary. Also, the front view is necessary to show 
the notch in the tenon, and the left side view to show the bead. 

As stated under Plate 8, the right and left side views convey 

110 



PENCIL MECHANICAL DRAWING 



111 



the same information and therefore either may be drawn. The 
one is usually selected which requires the fewer dotted lines. 
Example: Comparing Fig. 113, A and B, the right side view is 
preferable for this reason. Ordinarily the right or left side view 
is drawn opposite the front view In some cases, however, a 
better arrangement will be secured by placing the side view oppo- 



3f 



ED 






\ 




1 



a 



X 




1 



3 



^ 



E 



ffa C 



-\ 


1 



Fig. 113. Relation op Front, Top, and Side Views 

site the top view instead of opposite the front view. Fig. 113, 
C and D. In this case the views are so related that horizontal 
distances from front to back, which are common to the top and 
side views, may be projected from one view to the other. 

To relate properly the side view to the front view of an object, 
attention should be given to the following conditions: 

1. In all cases the side views of the front surfaces are adjacent 
to the front view of the object. Example : M N and P in Fig. 
113 represent the side views of the front surface. 



112 



MECHANICAL DRAWING 



2. In securing the views of an object, one should never move 
the object hut should himself move from the position taken in 
securing a front view, viz., to the left, to secure the left side view 
or to the right to secure a right side view. 

The student should test his knowledge of the orthographic 
principles just stated by answering the following questions: 
See Fig. 114. 

1. (a) Why is the top view of the object necessary ? (b) The 
front view? (c) The right side view ? 



I 



O 



B 



j_ 



— r 
I 
I 

-4. 
I 
I 
I 



-I— 



Fig. 114. Eeview Problem 



2. (a) Is the right side view preferable to the left side view? 
(b) Why? 

3. (a) Where is the near horizontal edge 5, 6, shown in the 
top view? (b) In the front view? 

4. (a) Where is the vertical surface 5, 8, shown in the front 
view? (b) In the top view? 

5. (a) Where is the back vertical surface 1, 2, 3, 4, shown in 
the side view? (b) In the top view? 

6. Draw the right side view opposite the top view. 

7. Draw the left side view opposite the front view. 

8. Draw the left side view opposite the top view. 



PENCIL MECHx\NICAL DRAWING 



113 




Fig. 115. Type Problem. Perspective of Sash Joint 

In this chapter an orthographic sketch will be required pre- 
ceding each mechanical drawing. This freehand practice will 



l: 



3: 



Fig. 116. Type Problem. Constructive Stage of Pencil Mech. Drawing 





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o 


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o 


UJ 


T 


O 


(D 




< 




(/} 



u 



I 



PENCIL MECHANICAL DEAWING 



115 



develop further skill in orthographic sketching and will make 
the student familiar with the problem. As a result time will be 
saved in making the mechanical drawing, 

DATA FOR DRAWING PLATE 12 

Given: Perspective sketches, Figs. 118, 119, and 120. 

Required: To draw a three view orthographic sketch of 
the object shown in Fig. 118, 119, or 120, or any similar object 
with dimensions, as assigned by the instructor. 




Fig. 118. Mortise 



Instructions: 

1. This sketch should be drawn entirely freehand. Propor- 
tions and distances should be estimated — not measured. 

2. Consider the form of the object carefully and select the 
views to be drawn. 

3. Compare the over-all dimensions of each view and block in 
the view by drawing a rectangle the sides of which are in the 
proportions of the over-all dimensions of the object shown in this 
view. Example : In Fig. 117 the over-all dimensions of the object 
which are represented in the front view are 3f and If". The 
length of the sides of the rectangle are therefore drawn in the 



116 



MECHANICAL DRAWING 




Fig. 119. Milk Stool 



«:■ ^1 




Fig. 120. Concrete Flower Box 



PENCIL MECHANICAL DRAWING 117 

approximate ratio of 3^ :15=2 :1, or, in other words, the length 
of the rectangle is twice its width. The length of the top view 
is equal to the length of the front view. Its width is about 
one-fourth of its length. The height of the side view is equal to 
that of the front view. Its width is about one-half of its height. 
4. The distances from the views to the border line above and 
below the views should be equal and the distances from the views 
to the border lines at the right and left should be equal. Use the 
same principle for placing the views as given for the problems 
of Chapter II, page 81. 




Fig 121. Lettering Plate 12 

5. When the rectangles are properly located, sketch in lightly 
the details of each view, proportioning them by eye. 

6. Complete the views by retracing the lines. 

7. With the advice and suggestions of the instructor, select 
the necessary dimensions and then draw extension and dimen- 
sion lines, arrowheads, and figures. 

DATA FOR LETTERING PLATE 12 

Given: Plate 12 to reduced size. Fig. 121. 
Required: To make the plate to an enlarged scale. 



118 MECHANICAL DRAWING 

PEEPARATORY INSTRUCTIONS FOR DRAWING PLATE 13 

The following is a list of materials needed in making the 
pencil mechanical drawing in this chapter : 

1. Drawing board. 

2. High-grade paper similar to Duplex or Cream, 11" x 15" 
slieets. 

3. T-square. 

4. 30°-60° and 45° triangles. 

5. High-grade 5H pencil. 

6. Scale. 

7. Bow compass. 

8. 4H compass lead. 

9. Pencil pointer. 

10. Eraser. 

11. Erasing shield. 

The Drawing Board. The best boards are designed to pre- 
vent warping, various means being used to accomplish this end. 
Some are built of narrow strips glued together; others have a 
series of saw cuts running lengthwise with the grain to reduce 
the transverse strength. Fig. 122. Such boards are made rigid 
by cleats of hard wood screwed through oblong slots fitted with 
metal bushings to the back of the board. This construction 
allows the board to expand and contract, the screws sliding in 
the slots. 

For accurate work it is necessary that the edge of the board 
against which the head of the T-square is placed be perfectly 
straight and that the face of the board lie in a plane. To test 
the edges of the board, place on each a standard straightedge 
or the edge of a T-square blade which is known to be straight. 
An edge of the board is straight if, when held up to the light, 
the straightedge is in contact at all points. 

The surface of the board may be tested in like manner by 
placing the straightedge upon it in various positions. 

The edges and surface of the board should be kept free from 
cuts, scratches, and bruises. The board should not be subjected 
to extremes of temperature or moisture. 



PENCIL MECHANICAL DEAWING 



119 



Drawing Paper. ¥ov mechanical drawing, where a sharp, 
fine line is to be produced with a hard pencil, a tough, hard paper 
should be used. It should stand considerable erasing without 
injury to the surface. It should not become brittle or discolored 
from reasonable exposure or age. If freehand lettering is to be 
done the surface must be reasonably smooth to secure the best 
results. If considerable time is to be spent on a drawing, a 





Fig. 122. Drawing Boards 



paper should be selected which has an agreeable tint and which 
will not soil easily with handling. The paper used for the 
mechanical drawings of this course must fulfil these requirements. 

The drawing paper should be fastened to the board in the 
upper left corner of the board as for sketching. After inserting 
the first tack, make the upper edge of the sheet horizontal by 
means of the T-square ; stretch the sheet and insert the remaining 
thumb tacks in the usual manner. 

The T-square is used to draw horizontal lines and to provide 
an edge against which the triangles are placed. It consists of a 



120 MECHANICAL DRAWING 

rule called the blade, attached to one end of which is a cross- 
piece called the head. Fig. 123. The head is sometimes i^istened 
to the blade by means of a swivel, so that the blade may be set 
at any desired angle. 

T-squares are made of steel, hard rubber, and wood. The 
steel blade is the most accurate but tends to soil the drawing. 
For ordinary work wooden blades are preferable. They are 
usually made of maple, mahogany, or pearwood, and their edges 
are often lined with hardwood or celluloid. 




Fig. 123. T-Square. Plain and Swivel Head 

The celluloid edges make it possible to see lines near the one 
to be drawn and are therefore quite convenient when joining 
lines at corners, etc. 

The upper or working edge of the T-square and the edge of 
the head which rests against the drawing should be perfectly 
straight. The edge of the blade may be tested as follows : 

1. Draw a long line along the edge of the blade. 

2. Reverse the ends of the blade with respect to the ruled line, 
keeping the same side up and bringing the same edge against the 
ruled line. 

3. Draw a second line along the edge of the blade. If the 
edge of the blade is straight the two lines will coincide. Both 
the head and the blade of the T-square may also be tested by 
means of a straightedge. Since the T-square is used only for 
ruling parallel lines, and as lines at other angles are drawn with 
the triangles in combination with the T-square, it is evident that 
the accuracy of the angles beween lines drawn with the T-square 



PENCIL MECHANICAL DRAWING 



121 



and those drawn with the triangles does not depend upon the 
angle of the blade to the head of the T-square. It is not neces- 
sary, therefore, that the edge of the head and blade be exactly 
at an angle of 90° to each other. 

Care should be taken to preserve the upper edge of the blade 
of the T-square from injury. It should never be used as a guide 
for the knife in cutting paper. When using the T-square the 
head is pressed firmly against the edge of the board with the left 




Fig. 124. Ruling a Horizontal Line 



hand as shown in Fig. 124. The lines are always drawn along 
its upper edge. 

The triangles are used in combination with the T-square for 
drawing lines at certain angles to the horizontal. They are used 
in combination with each other for drawing lines at various 
angles with lines which are not horizontal. 

Triangles are made of steel, wood, hard rubber, or celluloid. 
Steel triangles are used for the most accurate work. Triangles 
made of wood are easily injured and are likely to change their 
shape. Those made of celluloid have the advantage of being 
transparent and are more generally used. For accurate work it 
is necessary that the edges of the triangles be straight and that 



122 



MECHANICAL DRAWING 



the angles be true. The edge may be tested by the method given 
for testing the T-square. 

Assuming that the edge of the T-square has been found to be 
straight, the 90° angle of a triangle may be tested as follows : 

1. Place the triangle in position D, as shown in Fig. 126, and 
draw the line AB. 




Fig. 125. Euling a Vertical Line 



2. If when the triangle is turned over into position C, the 
vertical edge coincides with the line A B, the angle is 90° 

3. When the 90° angle of the 45° triangle has been found 
true, the 45° angles are true if equal. 

Compare the two 45° angles as follows, Fig, 127 : 

1. Place the triangle against the T-square and draw a 45° 
line. 

2. Turn the triangle over so that the other 45° angle comes 
into the position previously occupied by the first. If the edges 
of the triangle coincide with the line drawn, the 45° angles are 
equal. 

The 60° angle of a 30°-60° triangle may be tested as follows: 

1. Draw a horizontal line, A B, along the T-square. Fig. 128. 

2. Draw a 60° line, B C, along the edge of the triangle cross- 
ing the horizontal line. 

3. Turn the triangle over and draw a second 60° line, AC, 



PENCIL MECHANICAL DEAWING 



123 



completing a' triangle. If the triangle formed is equilateral, the 
60° angle is true. 

The lengths of the sides of the triangle may be compared by 
means of the dividers. When the edges are straight and the 90° 




o o 
o o 




o 



Fig. 126. Testing the 90° Angle 



o o 
o o 





o 



Fig. 127. Testing the 45° Angle 
Fig. 128. Testing the 30° and 60° Angles 

and 60° angles are found to be true, the remaining angle, 30°, 
will also be true. 



124 MECHANICAL DRAWING 

With the 30°-60° triangle, lines may be drawn at 90° to the 




Fig. 129. Lines Drawn 

WITH THE 30°, 60° 

Tkiangle 



Fig. 130. Lines Drawn 
WITH the 45° Triangle 




Fig. 131. Lines Drawn with a Combination of the 30°, 60° and 45° 

Triangle 

horizontal and at 30° or 60° with the horizontal to the right and 
to the left. Fig. 129. With the 45° triangle, lines may be drawn 



PENCIL MECHANICAL DRAWING 125 

at 90° to the horizontal and at 45° with the horizontal to the right 
or to the left. Fig. 130. 

By combining the two triangles, lines may be drawn at 15° 
or 75° with the horizontal to the right and to the left. Fig. 131. 

Lines parallel to any given line may be drawn by placing the 
two triangles in contact and sliding them as one tool until an 
edge of one coincides with the given line. Fig. 132. With 
triangle A held firmly in place, triangle B may be moved along 
it and lines drawn parallel to the given line. 





Fig. 132. Lines Drawn Parallel or Perpendicular to Any Given Line 



Lines perpendicular to the given line may be drawn along 
the edge of triangle B which is at 90° to the given line. 

The direction in which lines should be drawn along the 
triangles is shown in Figs. 129 and 130. The forearm should 
always make a right angle with the line being drawn. 

The edges of the triangles should not be cut or bruised. If 
they are allowed to fall on the floor a corner may be blunted and 
as a result the angle will not be true. The celluloid triangles 
should not be allowed to remain bent for any length of time, 
as they will remain permanently so. 

Pencils. For mechanical drawing where it is desired to pro- 
duce fine sharp lines, a hard pencil should be used on a compara- 
tively smooth, hard surfaced paper. The pencil should not be 
sharp enough or used with enough pressure to crease the paper. 

The 5H pencil should be used for drawing lines mechanically. 



126 MECHANICAL DRAWING 

For convenience in using the pencil for different purposes, it 
should be sharpened at both ends. One end is used for ruling 
lines and the other for laying off measurements. The ruling 
point is obtained by cutting away the wood to expose about {'' 
of lead and by rubbing opposite sides of the lead on a sandpaper 
pad or file to produce a wedge-shaped point. Fig. 133. This 
point is used for ruling continuous lines. The measuring point 
is similar to the conical point used in sketching except that the 
point is sharper in order that very accurate measurements may 
be laid off with it. It is used both for measuring and making 
dotted lines. 

To insure accuracy in laying off measurements from the scale, 
the eye should be directly above the division on the scale from 



TTTT 



RULING POINT MEASURING POINT 



Fig. 133. Ruling and Measuring Joints of the Mechanical Drawing 

Pencil 

which the dimension is to be laid off. Care should be taken to 
place the point of the pencil on the paper exactly opposite the 
mark on the scale. The pencil should be revolved upon its axis 
while in this position without pressing the lead into the paper. 
The mark left by the pencil should be a small, round dot just 
visible to the eye. 

Ruling Horizontal Lines. In ruling horizontal lines the posi- 
tion of the hand is the same as for sketching horizontal lines. 
In this case, however, the pencil is held leaning slightly forward 
with the point in the position shown in Fig. 124. The line is 
drawn with a continuous motion to the right with the tip of the 
fourth finger touching the T-square to steady the hand. Fig. 124. 
The forearm should always be at right angles to the line being 
drawn. 

Vertical Lilies are drawn along the edge of a triangle which 
is set against the T-square as shown in Fig. 125, Note that the 



PENCIL MECHANICAL DRAWING 127 

triangle is to the right of the line. The line should be drawn 
away from the T-square with the hand and arm in the same 
relative position to the line being drawn as for horizontal lines. 
Scales are used for taking measurements and laying off dis- 
tances. They are made of paper, steel, and wood. Ordinarily 
scales are made of boxwood. There are two general forms, the 
flat and the triangular. The flat scale may have from one to four 
graduated faces and the triangular scale from four to six gradu- 
ated faces. The graduations are placed directly on the wooden 
face of the scale or the face is coated with a white compoimd 
which makes the graduation easier to read. 



■2-4^ 



wm 



iw 



wiw 



3 6 9 



Fig. 134. Eeadikg the Architect's Scale 

The faces of the scales are graduated as follows: 

The Engineer's Scale is divided to 10, 20, 30, 40, 50, and 60 
parts to the inch. It is full divided, i. e., the small divisions are 
marked off for the full length of the face. 

Tlie ArcJiitect's Scale is divided to g\, y^o, ^, |, §, ^, f, 1, 1|, 
and 3 inches to the foot. The edges on this scale are open di- 
vided, i. e., only the portion of the face representing one foot 
is subdivided to read in smaller units. One face of the scale is 
usually divided into iV" foi" its full length. 

To illustrate the reading of the architect's scale, consider the 
edge designated by a figure 1 at the end. Fig. 134. This indi- 
cates that one inch on this scale represents one foot. The inch 
to the right of the at the right end of the scale is divided into 
forty-eight equal parts so that each of the smaller divisions rep- 
resents I" and the spaces between the 0, 3, 6, and 9 represent 3" 
each. To the left of the 0, the readings 1, 2, etc., are inches, and 
therefore represent feet. To measure off 2'— 4-|" to the right of 
point X, place the 2 opposite the point and read four and one- 
half inches to the right past the 0. In case it is desired to lay off 



128 MECHANICAL DRAWING 

this distance to the left of Y, place the four and one-half inch 
mark opposite Y and read past the to the 2. 

The Proportional Inch Scale is divided to read one-half or 
one-fourth inch to the inch and has one face divided to ^V" foi" 
its full length. The open divided edges are read in the same 
manner as the architect's scale. The difference is that in this 
case the large divisions represent inches instead of feet. One of 
the large divisions is subdivided to read sixteenths. 

Drawing Instruments. In beginning mechanical drawing it 
is important that the student have a good set of instruments. It 
is difficult to define a "good" set of instruments, for the better 
grades are extensively imitated. The student should be guided 
in his selection either by some experienced draftsman or by the 
trademark and the price charged by a reliable dealer. 

A good set of instruments differs from a poor one, mainly, 
in the quality of materials used, correct tempering, and good 
workmanship. The steel of the pens must be properly tempered 
so that when once sharpened the points will remain in good con- 
dition for a reasonable time. The compass and dividers must be 
so made that they will retain their alignment and adjustment 
when handled with ordinary care. These qualities can only be 
definitely determined after the instruments have been given a 
fair trial. 

To secure uniformly satisfactory results in drawing it is 
necessary to start with a good set of instruments and to keep 
them in good condition. 

The Compass is used for drawing circles and arcs of circles. 
Fig. 135. The better grades are made of German silver. It is 
important that a compass be light yet rigid. The most impor- 
tant part of the compass is the head which, in the modern instru- 
ments, consists of two discs held in contact in a fork by means 
of pivot screws. By adjusting these screws the pressure between 
the discs is regulated. This pressure should be such that the 
legs of the compass may be opene'd or closed without springing 
them. On the other hand, the joint should be tight enough to 
retain the setting when the instrument is in use. 

The thing of next importance is the socket joint of the remove 
able pen and pencil parts. These are made in various forms. 



PENCIL MECHANICAL DRAWING 129 

They usually consist of a shank on the pen and pencil parts 
which fits into a corresponding socket in the compass leg. The 
proper position of the shank in the socket is insured hy some 
device such as a feather or sharp corner on the shank which is 
matched by a corresponding slit or groove in the socket. These 
parts are made to clamp together with a thumb screw or else a 
bayonet fitting is used. 




Fig. 135. Drawing a Circle with the Compass 

The legs of the compass should move in the same plane. To 
test the compass for alignment: 

1. Place the parts in the sockets. 

2. Bend the legs out at the head, and 

3. Bring the joints together, as shown in Fig. 136. If the 
points are exactly together the joints are true. 

Before using a compass, the needle point and lead should be 
adjusted as follows: 

1. Place the pen in the compass and adjust the needle point 
so that it projects slightly beyond the nibs of the pen. 

2. Eemove the pen. 

3. Replace the pencil and adjust the head so that it is slightly 
shorter than the needle point. The pen and pencil parts are 
now interchangeable without adjusting the needle point. 



130 



MECHANICAL DRAWING 



In using the compass proceed in the following manner : 

1. Place a 4H lead in the compass and sharpen it to a narrow 
wedge, in width about one-half the diameter of the lead. 

2. Set the lead so that it projects about one-half the length 
of the needle point beyond the shoulder. 

3. Draw the center lines of the circle to be drawn at right 
angles and lay off the radius on one of them. 




Fig. 136. Testing the Compass 

4. Grasp the compass by the handle between the thumb and 
first finger of the right hand. Care should be taken to place the 
needle point exactly at the intersection of the center lines. 

5. Adjust the lead to the exact radius and draw the circle, 
rolling the handle of the compass between the thumb and finger. 

The large compass should not be used for circles of less than 
f '' radius. For very large circles the lengthening bar should be 
inserted between the leg of the compass and the pen or pencil 
point. When this does not suffice a beam compass should be used. 

Dividers are similar to compasses in general appearance. The 
legs terminate in sharp steel points. The dividers are used for 
laying off distances from the scale, for transferring lengths, or 
for dividing straight or curved lines into any number of equal 
parts. 



PENCIL MECHANICAL DRAWING 



131 



To divide a line into any number of equal parts with the 
dividers, proceed as follows: (Assume that the line is to be 
divided into three equal parts.) 

1. Open the dividers to what is estimated to be one-third the 
length of the line. 

2. Step off the estimated distance three times on the line. 




Fig. 137. Stepping Off with the Dividers 



3. Adjust the dividers to one-third the error making the dis- 
tance between the points larger or smaller as the case may- 
require. 

4. Repeat the process until the third step ends exactly at the 
end of the line. In taking the steps the dividers are held by the 
handle between the thumb and first finger and swung alternately 
first to one side of the line and then the other as shown in 
Fig. 137. This avoids rolling the handle in an awkward position 
between the thumb and finger. 



132 



MECHANICAL DRAWING 



The Bow Pen, Bow Pencil, and Bow Dividers. The bow pen 
and bow pencil are used to describe small circles, and the bow 
dividers to lay off small distances. They have the advantage over 
the larger instruments that they retain their adjustment. There 
are two forms of adjusting devices, as shown in Fig. 138. To 
make large adjustments in the instruments having side screws the 
pressure on the nut should be relieved by pressing the legs to- 
gether with the left hand while the nut is made to spin with the 
first finger of the right hand. 




Fig. 138. Center and Side Screw Adjustment of Bow Instruments 



The bow compass should be used in the same manner as the 
large compass, as described on page 129. 

The Eraser. Ordinarily a medium hard eraser such as the 
ruby is used for removing pencil lines from a drawing. A soft 
flexible eraser is very satisfactory for cleaning a pencil drawing 
without erasing the lines. When erasing lines the paper near the 
lines to be erased should be held down with the thumb and first 
finger of the left hand to prevent it from crumpling. 

The Erasing Shield is used to protect the parts of the draw- 
ing which are not to be erased. The opening in the shield is 
selected which is best suited to expose only the parts to be erased. 
The shield is held in position on the drawing with the thumb and 



PENCIL MECHANICAL DRAWING 133 

first finger of the left hand, while the eraser is applied with the 
right. Fig. 139 

Steps in Making a Mechanical Drawing 

The Border Rectmigle. To draw the border rectangle, proceed 
as follows: 

1 Lay off I" from the upper and left hand edge of the sheet. 

2, Through the points thus located draw the upper and left 
hand sides of the border rectangle. 




Fig. 139. Usixg the Eraser and Shield 

3. On these lines, and from their intersection, lay off 14" to 
the right and 10" downward. 

4. Through the points thus found draw the remaining sides 
of the border rectangle. 

The Enclosing Rectangle. In mechanical drawing the views 
are located centrally by calculating the position of a rectangle 
in which they may be inscribed. In this course the distance 
between views should not be less than f " or more than 1". The 
student's calculation should be made as indicated in Fig. 140. 

Accuracy. It is of prime importance that a mechanical draw- 
ing be accurate. Accuracy depends both on the quality and con- 
dition of the instruments and materials and upon the skill of 
the draftsman. All straightedges, angles, etc., should be tested 
as just described. When the tools are found to be in good con- 
dition the draftsman should take great care to lay off measure- 



r~ 



^ Border l/ne 



7 



T 



3"- 



* 3 



(3 =■ "^ 










Fig. 140. Calculation for the Size and Position of the Enclosing 

EeCT ANGLE 

(134) 



PENCIL MECHANICAL DRAWING 135 

ments accurately, and draw the lines exactly through the points 
located. It is always well to place the point of the pencil in the 
located point, bring the straightedge up to the pencil, and then 
draw the line, being careful to maintain the same relationship 
throughout between the pencil and the straightedge. 

Errors multiply with the number of operations involved, 
hence, other things being equal, the most direct construction is 
the most accurate one. 

Constructive Stage. In this stage all measurements are laid 
off and lines drawn lightly and of indefinite length. This is what 
is sometimes known as the blocking-in stage. "When using the 
scale make as many measurements as possible. "Whenever prac- 
ticable, consecutive measurements should be laid off with the 
scale in one position. Be as systematic as possible in making 
measurements and in using the T-square and triangles. It is a 
good plan to draw as many of the horizontal lines as may be 
drawn at one time, beginning at the top and moving the T-square 
downward. In like manner draw vertical lines, several at a time, 
moving the triangle from left to right. The lines should be 
drawn long enough so that there will be no need to extend them. 

No distinction is made between visible and invisible edges in 
this stage. Fig. 116. 

FinisJiing Stage. In this stage the drawing is completed as it 
will finally appear. First, erase all lines not needed in the fin- 
ished drawing and, second, retrace all required lines with a care- 
fully sharpened 5H pencil. All finished lines must be of uniform 
width and shade. They must be ended at the proper points. 
The lines should be drawn in the following order: 

1, Horizontal lines beginning at the top of the sheet. 

2. Vertical lines beginning at the left of the sheet. 

The hidden edges of the object should now be represented 
by so-called dotted lines, which in reality are lines made up of 
short dashes and spaces. The dashes are |" long, separated by 
aV spaces. Fig. 76. The end of each dash can be made distinct 
by keeping the end of the pencil in contact with the paper until 
the end of the line is reached. The pencil should be placed upon 
the paper, drawn -g" on the paper, stopped, and then raised in 
making each dash. 



136 MECHANICAL DRAWING 

Dimensioning. The draftsman's judgment is used more in 
dimensioning than in any other part of the drawing. To avoid 
mistakes and to facilitate the work of the mechanic, only neces- 
sary dimensions should be given. They should be placed in such 
a way as to make the drawing easily read. Cases are rare where 
it is advisable to repeat the same dimensions on different views. 
Repeating dimensions adds to the difficulty in checking them and 
when changes are made there is a possibility of making a change 
in one place and not in another. This leads to confusion. Plac- 
ing dimensions in obscure and out of the way places should be 
avoided. Whenever possible, dimensions should be grouped in 
such a way as to make their relation obvious. It should not be 
necessary for the mechanic to do any calculating to obtain 
necessary dimensions. 

No doubt, the best guide to follow, in placing dimensions on 
a drawing, is for the draftsman to imagine himself in the me- 
chanic 's place and to consider the operations through which the 
object must go to become a finished product. With this idea in 
mind most problems in dimensioning will be solved without diffi- 
culty. For example, when a machinist drills a hole he sets the 
point of the drill at its center ; hence the hole should be dimen- 
sioned by referring its center to some surface, line, or point easily 
accessible. 

In ordinary working drawings, dimensions are usually given 
in inches up to twenty-four inches. Above twenty-four inches 
they should be given in feet and inches. Examples : 23^", 2'-4y . 

For all ordinary work, fractions in dimensions containing 
mixed numbers have the following denominators : 2, 4, 8, 16, 32, 
64 ; such denominators as 6 or 19 are not used. When very small 
fractions of an inch are necessary, as in the case of special fits, 
etc., the fractional part of an inch may be expressed in decimals 
of three or four places. Example : 5.006'' bore. 

Extension and Dimension Lines. The extension lines and 
dimension lines should be drawn in the order suggested for the 
finishing stage of the pencil drawing, i.e., draw all horizontal 
lines beginning at the top and rnoving downward, then draw all 
vertical lines beginning at the left and moving toward the right. 
As in orthographic sketching, the extension lines should begin 



PENCIL MECHANICAL DRAWING 137 

about aV" from the outline of the object and continue I" beyond 
the arrowheads. The space between the outline of the object and 
the nearest dimension line, or between two parallel consecutive 
dimension lines, should be about I". Th^ extension and dimen- 
sion lines in pencil should be of the same width and shade as the 




Fig. 141. Showing Actual Heights of Whole Number and Fraction 

object lines. Center lines may be used as extension lines, but 
not as dimension lines. 

The Dimension Figures and Notes. If a drawing is to present 
a neat appearance, a suitable type of letter and figure should be 
used for all notes and dimensions. A very plain letter should be 
selected; one that can be drawn with reasonable rapidity and 
that will be in harmony with the remainder of the drawing. It 
is essential that a standard height be adopted and adhered to for 
all notes and figures on the drawing. For this course the stand- 
ard height for the whole number is |'' and the total height of the 
fraction ^^ as shown in Fig. 141. Whenever possible, notes 
should be lettered on horizontal guide lines. The letters should 
be 3^" high. To insure uniform heights for all notes the distance 
between the ruled guide lines should be accurately laid oif with 
the scale or stepped off with the dividers. 

As nearly as possible, place the dimension figures in the cen- 
ter of the dimension line, leaving a convenient free space for the 
figures. Whenever a center line interferes with the dimension 
figures, place it near the center line and either to the right or 
left of it. In the case of consecutive parallel dimension lines 
where the dimension figure in one line would naturally interfere 
with the dimension figure in the other dimension line, the dimen- 
sion figures should be "staggered"; that is, one dimension figure 
should be placed a little to the right and tlie other to the left of 
the center of the dimension line, so that they will not interfere. 
Example: Fig. 147. 



138 



MECHANICAL DRAWING 



Information which the dimensioned drawing does not make 
clear is put into the form of notes. They usually relate to mate- 
rials, finish, number of parts needed, etc. Example : See note 
below the view. Fig. 156. 

The Title. The views of an object with their dimensions and 
notes do not convey all of the necessary information. A title 
which supplies the deficiency is therefore added. The title is 



NAME OF OBJECT REPRESENTED 



* [«. i" 4^ .s"_»j^ S"^!— 



Fig. 142. Dimension and Position of Items in Title Block 

usually placed in the lower right-hand corner of the sheet so that 
it will be easily accessible when the drawing is filed. 



/Z TAIL 

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TAIL ^TOCK 

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Fig. 143. Showing Method of Balancing the Lines in the Title 



Various elements may enter into the title, depending upon 
the character of the drawing and the use to be made of it. The 
following items are usually found in the titles of commercial 
drawings of machines or structures: 



PENCIL MECHANICAL DRAWING 



139 



1. Name of part or parts of machine or structure. 

2. Name of complete machine or structure. 

3. Manufacturer's firm name and address. 

4. Drawing number. 

5. Date of finishing drawings. 

6. Scale to which drawing is made. 

7. Initials of draftsman, tracer, and checker. 











NOTICE TO SHOP 


PC. NO. 


P*TT. (10. 


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ALL RIQHTS OF DESIGN OR INVENTION ARE RESERVED. 



Link- Belt Company 

PHILADELPHIA CHICAGO INDIANAPOLIS 



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ORDER NO. 



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Fig. 144. Commercial Titles 



The titles of the plates given in this chapter will be much 
simpler than the ordinary commercial title. Figs. 142 and 143 
show two forms of title suitable for this course. The words for 
each title in this chapter will be given below the figure from 
which the drawing is made. 

The relative importance of the items of a title is shown by 
the varying heights or weight, or both, of the letters. In some 



140 MECHANICAL DRAWING 

drafting offices a rubber stamp is used on the pencil drawing to 
obtain the words and lines that are common to all drawings. The 
same words and lines are often printed on the tracing cloth in 
type. Example : Fig. 144. The style of letter used should be 
plain and dignified, whether printed in type or drawn freehand. 

The Title Block. The title for each mechanical drawing plate 
in this course will be placed in a title Mock. The dimensions for 
this block with the names and position of the items are shown in 
Fig. 143. The height of the letters and spaces between lines of 
letters are shown in Fig. 143. 

Balancing a Title. It is essential to the appearance of a title 
that the lines be symmetrical with respect to a vertical center 
line. Example : Fig. 143 shows a title properly balanced. 

To balance the title proceed as follows : 

1. Tack a piece of drawing paper to the board opposite the 
lower right hand corner of the sheet. Fig. 143. This will be 
referred to as the trial sheet. 

2. Draw a line as a continuation of the lower border line on 
the trial sheet. This is a base line for measurements. 

3. Lay off on the trial sheet the space for the letters as given 
in Fig. 143. Extreme accuracy in making these measurements 
is necessary, as the width of the letters varies with their height. 
A small error in height makes the letter appear much too large 
or too small. 

4. Eule each guide line on the trial sheet and the drawing 
sheet with one setting of the T-square. Care should be taken to 
draw exactly through the points located. Check the heights of 
the spaces with the scale. 

5. Letter each line of the title on the trial sheet, giving 
attention to the proportion of the letters and to spacing. Do not 
try to balance the lines on this sheet. 

6. Locate the middle point of each line on the trial sheet. 

7. Draw the vertical center line of the title through the 
center of the title rectangle. 

8. Cut out each line of letters from the trial sheet and place 
it above the space in which it is to be lettered on the drawing 
sheet, with its middle point on the center line of the title. 



PENCIL MECHANICAL DRAWING 141 

9. Letter each line, following the spacing on the trial line. 
The result should he a perfectly balanced title. 

DATA FOR DRAWING PLATE 13 

Given: The orthographic sketch, Plate 12, 
Required: To make a pencil mechanical drawing from 
Plate 12. 

Instructions : 

1. Test the drawing board, T-square, and triangles as ex- 
plained under the corresponding headings in this chapter. 




Fig. 145. Lettering Plate 13 

2. Draw the border line as previously explained. 

3. Calculate the size of the enclosing rectangle. 

4. Lay off as many of the dimensions of the object as possible 
at one time. Draw the lines lightly. 

5. Check the drawing for accuracy. 

6. Erase unnecessary lines and retrace the drawing, taking 
eare to end the lines exactly at their intersections. Dot the lines 
representing hidden edges. 

7. Draw extension and dimension lines and put in dimensions. 



142 



MECHANICAL DEAWING 



8. Letter a note, giving the number of parts required and 
the material from which they are to be made. 

9. Letter the title, using the nam.e of the object given below 
the figure from which the drawing was made. 

DATA FOR LETTERING PLATE 13 

Given: Plate 13 to reduced size. Fig. 145. 

Required: To make the plate in ink to an enlarged scale. 




Fig. 146. Type Problem. Perspective of Brace 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 14 

In this plate the student will need to decide for himself the 
number of views necessary, and their arrangement, to show the 
form of the object. It is suggested that for this purpose he 
review the principles given on pages 110 and 111. 



PENCIL MECHANICAL DRAWING 



143 



The methods of dimensioning, particularly those relating to 
the dimensioning of inclined lines, should also be reviewed. 
Pages 136 and 137. 




B 



DETAIL 
BRACE JOINT 



!■-' I^-"I 



SCALE- FULL SIZE 



Fig. 147. Type Problem. Detail of Brace Joint 




Fig. 148. Vise Anvil 



DATA FOR DRAWING PLATE U 



Given: Perspective sketches, Figs. 148, 149, 150, and 151. 
Required: To draw an orthographic sketch of the object 




Fig. 149, Towel Hanger 




(144) 



Fig, 150, Feed Hopper 



PENCIL JMECHANICAL DK AWING 



14^ 



shown in Fig. 148, 149, 150, or 151, or any similar object, with 
dimensions, as assigned by the instructor. 

Instructions: Proceed as for previous orthographic sketches. 




Fig. 151. Bird House 

DATA FOR LETTERING PLATE 14 

Given: Plate 14 to reduced size. Fig. 152. 

Required: To make the plate in ink to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 15 

Inclined Lines. Lines at such angles as 15°, 30°, 45°, 60°, 
and 75° may be drawn with the T-square and triangles described 
on pages 123 and 124. When the inclination of a line is not 
given in degrees at least two points on it must be located. The 
line is then drawn by placing an edge of a triangle or the 
T-square so that it passes through the two points. 

Scale. When an object is too large to be drawn full size on 
the sheet, it may be drawn to some fraction of the actual size. 



146 MECHANICAL DRAWING 

Half and quarter sizes are common scales for shop drawings. 
The edge of the scale, graduated to read half or quarter size, 
should be used instead of dividing the dimensions by 2 or 4. 
See page 127 for a description of the method of using the scale. 




Fig. 152. Lettering Plate 14 



DATA FOR DRAWING PLATE 15 



Given: The orthographic sketch, Plate 14. 
Required: To make a pencil mechanical drawing from 
Plate 14. 

Instructions: 

1. Draw the border line and calculate the size of the enclosing 
rectangle as in plate 13. 

2. Lay off the dimensions of the object and complete the con- 
structive stage. 

3. Check carefully each dimension for accuracy. 

4. Retrace the object lines, drawing (1) horizontal lines, 
beginning at the top; (2) vertical lines beginning at the left; 
(8) inclined lines. 

5. Draw extension and dimension lines and put in dimensions. 

6. Letter a note, giving the number of parts required and the 
material from which they are to be made. 



PENCIL MECHANICAL DRAWING 147 

7. Letter the title, using tlie name of the object given below 
the figure from which the drawing was made. 




Fig. 153. Lettering Plate 15 
DATA FOR LETTERING PLATE 15 

Given: Plate 15 to a reduced size. Fig. 153. 

Required: To make the plate in ink to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 16 

In a freehand or mechanical drawing where a straight line is 
tangent to an arc, the arc should be drawn first. In the con- 
structive stage the arc should be drawn long enough so that it 
will extend beyond the point of tangency when the line is drawn. 
A straightedge may then be laid tangent to the arc and the 
straight line drawn in. Before the drawing is finished the 
unnecessary part of the arc is erased. Fig. 155. 

Centers for rounded corners, fillets and other arcs of circles, 
which do not have their centers on any line of the drawing, are 
located by what is called the ' ' trial and error ' ' method. The 
compass should be first adjusted to the proper radius. To locate 
the center of the arc, set the lead on the tangent line at A, Fig. 



148 



MECHANICAL DRAWING 




Fig. 154, Type Problem. Perspective of Bearing 




Fig. 155. Type Problem. Constructive Stage of Mechanical Dravping 



150 MECHANICAL DRAWING 

157, estimating A C as nearly as possible equal to the radius of 
the arc. Set the needle point at B opposite A and bring the lead 
around to D. Move the needle point parallel to A C an amount 
equal to the error. The compass should then be again rotated 
back to A to test for accuracy, and if necessary further adjust- 
ment should be made before drawing the arc. 



I 
I 



Fig. 157. Trial and Error Method of Locating Centers 

Radius Dimensions. The dimension form for radius dimen- 
sions is shown in Fig. 189. "When the distance between the arc 
and its center is great enough to admit the figures and arrow- 
heads the form is as shown in Fig. 189. Sometimes a small cir- 
cle is drawn around the center in place of an arrowhead. This 
circle should be made freehand and about yg" i^i diameter. When 
the distance between the arc and its center is short the center, 
as shown by the |'' radius, is not indicated. Fig. 189. 

DATA FOR DRAWING PLATE 16 

Given: Perspective sketches. Figs. 158, 159, and 160. 

Required: To draw an orthographic sketch of the object 
shown in Fig. 158, 159 or 160, or any similar object, with dimen- 
sions, as assigned by the instructor. The student should decide 
what views are necessary to show the form of the object. 

Instructions : In drawing the circles and ares, sketch in the 
center lines and lay off the radii on each, as in Plate 10. 

PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 16 

Composition. This and the following plates will be devoted 
to the practice of notes which frequently appear on the drawing 
to give information not shown by the views. 



PENCIL MECHANICAL DRAWING 



151 




Fig. 158. Stuffing Box Gland 




Fig. 159. Stationery and Ink Stand 



152 



MECHANICAL DRAWING 



DATA FOE LETTERING PLATE 16 

Given: Plate 16 to reduced size. Fig. 161. " 

Required: To make the plate in ink to an enlarged scale. 




Fig. 160. Clamp 



DATA FOR DRAWING PLATE 17 

Given: The orthographic sketch, Plate 16. 
Required: To make a pencil mechanical drawing from 
Plate 16. 

Instructions : 

1. Draw the border line and enclosing rectangle. 

2. Locate and draw two center lines at right angles to each 
other for each arc or circle. 



PENCIL MECHANICAL DRAWING 153 

3. Draw the arcs of indefinite length so they extend beyond 
the points of tangency, 

4. Draw the straight lines tangent to the arcs. 

5. When the constructive stage is complete retrace the lines 
in the following order : (1) circles and arcs ; (2) horizontal lines, 
beginning at the top of the sheet; (3) vertical lines, beginning at 
the left of the sheet; (4) inclined lines. 



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Fig. 161. Lettering Plate 16 

6. The center line may be produced and used as an extension 
line where appropriate. 

?. Letter a note, giving the number of parts required and 
the materials from which they are to be made. 

8. Letter the title. 



DATA FOR LETTERING PLATE 17 

Given: Plate 17 to reduced size. Fig. 162. 

Required: To make the plate in ink to an enlarged scale. 



154 MECHANICAL DRAWING 

Review Questions 

1. (a) Wliat determines the number of views of an object? 
(b) When are more than two views necessary? 

2. Where is the front surface of an object represented in the 
side view? 

3. (a) What dimension is common to the top and side views? 
(b) If only the top and side views were drawn how should they 
be related ? . 





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Fig. 162. Lettering Plate 17 

4. What are the requisites of a good drawing board? 

5. (a) Describe a method for testing the surface and working 
edge of a drawing board, (b) What care should be taken of 
the surface and working edge of a drawing board ? 

6. Give requisites of a good T-square and explain its uses. 

7. Is it necessary for the head of a T-square to be at right 
angles to the blade ? Why ? 

8. Describe a method for testing the working edge of a 
T-square for straightness. 

9. (a) Describe the position of the T-square for drawing 
horizontal lines, (b) How is it held? (c) Illustrate by a sketch 
the position of the pencil in ruling a line along the T-square. 



PENCIL MECHANICAL DRAWING 155 

10. Describe the process of squaring and fastening the paper 
on the board for a mechanical drawing. 

11. What is the advantage of the celluloid triangle over tri- 
angles made of other materials ? * 

12. (a) For what are triangles used? (b) For what angles 
are they usually cut ? 

13. Describe a method of testing the accuracy of a 90° angle 
of a triangle. 

14. Describe a method of testing the accuracy of a 45° angle 
of a triangle. 

15. Describe a method of testing the accuracy of a 30° and 
60° angle of a triangle. 

16. (a) Show by a sketch how to construct an angle of 15° 
with a horizontal line by means of the T-square and triangles, 
(b) What angle does this make with a vertical line? 

17. (a) Show by a sketch how to construct an angle of 75° 
with a horizontal line by means of the T-square and triangles, 
(b) What angle does this make with a vertical line ? 

18. When using the triangle against the T-square in which 
direction should the line be drawn? (b) Show different cases 
by sketching. 

19. Show by a sketch how to draw a line parallel to any given 
line using only two triangles. Perpendicular. 

20. (a) Describe the positions of the T-square and triangle 
for drawing a vertical line, (b) In which direction is the line 
always drawn? 

21. (a) What is the shape of the ruling point of the pencil? 
(b) How is it obtained? (c) How does the measuring point of 
the mechanical drawing pencil differ from the point of the 
sketching pencil ? 

22. What are the uses of a scale in laying out a drawing ? 

23. Show by a sketch how to lay off a distance of 16' -3^", 
using the architect's scale ^'' to I'-O". 

24. How are the legs of the compass set for describing circles ? 

25. (a) What is the shape of the point of the lead used in 
the bow compass? (b) How should it be set with reference to 
the needle point ? 

26. (a) What is the range of the bow compass? (b) How 



156 MECHANICAL DRAWING 

are the circles drawn which are too large for the ordinary 
compass ? 

27. Show by a sketch how to divide a line into five equal parts 
by means of the dividers. 

28. Illustrate by a sketch and show calculations for deter- 
mining the size of an enclosing rectangle. 

29. Describe the process of drawing the border rectangle for 
a mechanical drawing sheet. 

30. (a) Define the constructive stage of the mechanical draw- 
ing, (b) How are hidden edges shown in this stage ? 

31. In what order are the lines drawn in the finishing stage ? 

32. (a) What space is left between the outline of the object 
and the end of the extension line? (b) How far should the 
extension line run beyond the arrowhead? (c) How far should 
the nearest dimension line be from the outline of the object? 
(d) How far apart should dimension lines be placed? 

33. (a) What is the height of the whole number in a dimen- 
sion? (b) The total height of the fraction ? 

34. What is the purpose of notes on a drawing ? 

35. What is the title block? 

36. Describe the steps taken in balancing two or more lines 
in a title. 

37. What dimension forms are used in showing the inclination 
of a line ? 

38. In what order are the lines drawn when an arc and a 
straight line are tangent to each other? 

39. (a) Show two ways of dimensioning a radius, (b) Under 
what condition is each used? 

DATA FOR REVIEW PROBLEMS 

Given: A perspective sketch, Fig. 163. 
Bequired : 

1. To make an orthographic sketch of the object shown in 
Fig. 163. 

2, To make a pencil mechanical drawing from the ortho- 
graphic sketch. 

Given: A perspective sketch, Fig. 164. 



PENCIL MECHANICAL DRAWING 



157 



Required: 

1. To make an orthographic sketch of the object shown in 
Fig. 164. 

2. To make a pencil mechanical drawing from the ortho- 
graphic sketch 

Given: A perspective sketch, Fig. 165. 
Required : 

1. To make an orthographic sketch of the object shown in 
Fig. 165. 




Fig. 163. Keyed Mortise and Tenon 



2. To make a pencil mechanical drawing from the ortho- 
graphic sketch. 



158 



MECHANICAL DRAWING 




Tig. 164. Toot Stool 




Fig. 165. Dash Pot Arm 



CHAPTER IV 



TRACING AND BLUEPRINTING 



Prospectus 



The pencil mechanical drawing of Chapter III is continued 
in this chapter to develop further skill in the use of instruments 
and to improve the technique in both the mechanical and free- 
hand elements of the drawing. It is the chief aim of this ehap- 

± 



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Fig. 166. Type Problem. Drawing Board 



ter to familiarize the student with the instruments, materials, 
and methods used in inking and to fix a standard for the ink 
drawing. As a result of the work of this chapter the student 
should be able to make neat tracings with proper width of lines, 
good joints, and uniform spacing in erosshatehing. The tech- 
nique of the lettering, arrowheads, and figures should be com- 
parable with that secured in the mechanical line work. 

159 




•liE^ . "" 



-j^--^i^ 



TRACING AND BLUEPRINTING 



161 



The tracing of the pencil mechanical drawing on tracing cloth 
with ink is usually the last step in the production of a drawing 
for the shop or for other purposes where a number of copies of 
the drawing are desired. The tracing is made on a transparent 
cloth or paper in order that the blueprints may be made from it 
as described later. The use of the blueprint makes it possible to 
have several copies of the drawing and at the same time preserve 
the original tracing from which other copies may be made at 
any time. 



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Fig. 168. Review Problem 



PEEPARATORY INSTRUCTIONS FOR DRAWING PLATE 18 



Inasmuch as the drawings of many objects require the use of 
sections, the student should review both the half and the quarter 
sections discussed in Chapter III, pages 98 and 99, and test 
his knowledge of the orthographic principles involved in making 
sectional views by answering the following questions. See Figs. 
99 and 168. 



162 



MECHANICAL DRAWING 



1. Where is the surface 1, 6, shown in the side view? 

2. (a) Does the rectangle 20, 21, 22, 23~ in the side view 
represent an opening or a solid part of the object? (b) Why? 

3. Where is the surface 7, 4 shown in the side and top views ? 

4. Make a front view of the object when cut on AB. 

5. (a) Is the side view affected by the section? (b) Top 
view ? 



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Fig. 169. Instrument Case 

Bach tracing in this chapter will be preceded by a pencil 
mechanical drawing. The pencil drawing is made to give the 
student additional practice in the handling of the instruments 
already used, to introduce the use of new instruments, and to 
provide drawings for the tracings. 



DATA FOR DRAWING PLATE 18 

Given: Orthographic drawings, Figs, 169, 170, 171. 

Required: To make a pencil mechanical drawing of the 
object shown in Fig. 169, 170, or 171 as assigned by the in- 
structor. The views given and required may be obtained from 
the following statements. Any similar problems may be substi- 
tuted by the instructor. 



TRACING AND BLUEPRINTING 



163 



Given: Fig. 169. The front, top, and right side views. 
Required: To draw the front, top, and left side half section 
views. 




Fig. 170. Medicine Cabinet 



Given: Fig. 170. The front and right side views. 
Required: To draw the front and left side half section 



views. 



Given: Fig. 171. The front and right side views. 
Required: To draw the front, and left side half section. 



Instructions : 

Proceed as for the mechanical drawing plates of Chapter III. 



164 



MECHANICAL DRAWING 



DATA FOR LETTERING PLATE 18 

Given: Plate 18 to reduced size. Fig. 172, 
Required: To make the plate to an enlarged scale. 




Sect/on showing consrructton 
of cushion 

Fig. 171. Foot Ktool 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 19 

The following is a list of the instruments and materials needed 
to make tracings and reproductions of mechanical drawings : 

1 . Tracing cloth. 

2. Tracing paper. 

3. Blueprint paper. 

4. Black waterproof ink. 

5. Ruling pen. 

6. Compass. 

7. Bow pen. 



TEACING AND BLUEPRINTING 165 

Tracing Cloth is a thin, firm cloth sized to hold ink and to 
make the cloth transparent. It is generally used when drawings 
are to be reproduced by the blue, black, or brown printing proc- 
ess. Drawings made on tracing cloth may be kept indefinitely 
if the cloth is kept dry and handled carefully. Changes may be 
made on the drawings and new prints made from time to time. 



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Fig. 172. Lettering Plate 18 

One side of the cloth is glazed and the other is dull. Either 
side may be used for inking. The glazed side will admit of the 
most erasing, but when inking is done on this side the cloth will 
curl. For work where penciling is to be done on the cloth, for 
drawings to be used for photographic reproduction, and for 
tinting, the dull side should be used. For the tracings of this 
chapter use the dull side. 

Sometimes the ink does not adhere readily to the surface of 
the cloth, particularly when the glazed side is used. To over- 
come this difficulty powdered chalk may be rubbed into the sur- 
face with a soft cloth. The chalk should be thoroughly removed 
before beginning inking. 

The cloth is fastened to the board with the same thumb tacks 
used to hold the pencil drawing. In order to avoid shifting this 



166 



MECHANICAL DRAWING 



drawing, the cloth should be spread over the sheet and one tack 
at a time removed and inserted through the cloth into the hole 
from which it came. 

Tracing Paper. For temporary drawings, especially where 
some portion of a drawing already made can be traced and used 
as part of a new drawing, a thin, transparent paper called 
tracing paper may be used with considerable saving of time. It 
should not be used for a permanent drawing or one which requires 
much handling. 




Fig. 173. Blueprinting Frame 



Blueprint Paper. Instead of sending the tracing into the 
shop where it would soon be injured or worn out, prints are 
made, usually on blueprint paper. This is a white paper covered 
with a solution which after being exposed to light, turns blue. 

The Blueprinting Process. To make prints, the inked side of 
the tracing is placed against the glass of a printing frame. The 
sensitized side of the blueprint paper is then placed against the 
tracing cloth and held firmly in contact with it. The contact is 
secured by means of clamps attached to the back of the board 
of the printing frame which holds both the tracing and the blue- 
print paper in place. Fig. 173. 

The printing frame should be placed in a direct light. If 
sunlight is used the exposure should be made during the middle 
of the day. The length of exposure to the light depends on the 
intensity of the sunlight or electric light and upon the "speed" 



TRACING AND BLUEPRINTING 167 

of the blueprint paper. After removing the paper from the 
frame it should be washed by turning it over several times in a 
basin of water. This removes the chemical on the sensitized side 
of the paper which was covered by the lines of the drawing on 
the tracing cloth and leaves the white paper exposed, forming 
the outline of the blueprint drawing. The result is a reproduc- 
tion of the drawing in white lines with a blue background. After 
the blueprint has been washed it should be hung vertically by one 
edge or over a horizontal stick to drain, and allowed to remain 
until it is dry. 

Black Ink will be used for all lines on the plates of this chap- 
ter. Black drawing ink is composed of finely divided carbon 
held in suspension in a liquid. When a line is drawn with this 
ink the liquid dries and leaves the carbon deposited on the paper 
or cloth. It is important that enough ink be left on the line so 
that when the ink is dry the amount of carbon deposited will be 
sufficient to make the line black. Thin ink gives brown lines. 
The liquid used in drawing ink evaporates quickly. The carbon 
therefore dries quickly, permitting one to work rapidly while 
tracing. The rapid evaporation of the ink necessitates keeping 
the stopper always in the bottle to prevent the ink from becoming 
too thick. 

The Ruling Pe7i is used more than any other instrument in the 
draftsman's outfit and should therefore be carefully selected. 
The steel of which the pen is made should be properly tempered 
and of such quality as to retain a smooth sharp edge. The blades 
should be of the same length, the inner one sufficiently stiff to 
resist a light pressure against the ruling edge. The nibs should 
be of the same width, equally rounded and directly opposite one 
another. The ends of the nibs should be narrow enough to give 
control in starting and ending lines, but broad enough to hold 
a reasonable amount of ink. When the nibs are too narrow the 
ink is drawn from the points by capillary attraction, making it 
difficult to start the ink at the beginning of a line. 

Filling and Using the Pen. The ruling pen should be ad- 
justed, filled, and used in the following manner : 

1. Adjust the pen by turning the thumb screw to approxi- 
mately the proper width of line. 



168 



MECHANICAL DRAWING 



2. Fill the pen by inserting the quill, attached to the stopper 
of the ink bottle, between the nibs of the pen. The pen should 
be filled to a height of about ^''. Care should be taken to avoid 
getting ink on the outside surfaces of the nibs. 

3. Set the pen to give the exact width of line required, testing 
it on the margin of the drawing or on a separate sheet. It should 
be tested on the same kind of surface as that on which it is to be 
used and by ruling along a straightedge — not freehand. 




Fig. 174. EuLiNG a Horizontal Line 



4. Hold the pen in the hand, as shown in Fig. 174, with the 
first finger above the thumb screw and the second finger against 
the right side of the pen. It should be held in a vertical plane, 
but may be allowed to lean slightly in the direction of motion. 
In this position both nibs will touch the cloth with equal pressure, 
W'hich is essential to the production of smooth, sharply defined 
lines. 

5. Draw rather slowly with a movement of the hand and arm, 
the forearm remaining perpendicular to the line being drawn. 
There should be no wrist movement, as the pen must not be 
rotated upon its axis. The tips of the third and fourth fingers 
should slide on the surface of the T-square or triangle to steady 
the hand. As the end of the line is approached the motion of 
the hand and arm should cease and the line should be completed 
with a finger movement. The center of the ink line on the tracing 
should be directly over the pencil line on the drawing being 



TRACING AND BLUEPRINTING 169 

traced. Care must be taken to set the pen exactly at the begin- 
ning of a line. At the end of a line the pen should be lifted 
vertically in order that the ink will not run out and cause the 
line to overrun. In drawing dotted lines, the pen must be set 
down vertically, the dash drawn, and the pen then lifted ver- 
tically so as to make both ends of the dash square. 

The spacing of section lines is done entirely by eye. In order 
to avoid varying the spaces the pen should be placed against the 
ruling edge and the perpendicular distance from the point of 
the pen to the last line drawn made equal to the perpendicular 
distance between any two sequential preceding lines. 

"When starling the crosshatching in a corner, there is a ten- 
dency to space the lines too closely, the spaces increasing as the 
lines become longer. The student should practice crosshatching 
rectangular areas on a scrap of tracing cloth before attempting to 
work on the drawing. 

Cleaning the Pen. The pen should be cleaned frequently by 
inserting a cloth at the side and pulling it out between the nibs. 
This should be done frequently while the pen is in use. The pen 
should not be laid away until the surfaces are thoroughly cleaned, 
as ink will corrode steel. If the ink does not start readily at the 
beginning of a line, squeeze the nibs of the pen together slightly 
to draw the ink down to the point. If the ink has been allowed 
to stand for some time, the pen should be cleaned and refilled. 
Do not touch the pen to the hand or a cloth to start the ink. 

Sharpening the Pen. The nibs of the pen should be as sharp 
as they can be made without producing the sensation of cutting 
when the pen is in use. They should not scratch the paper when 
drawing a line. This occurs if they are sharpened to a point 
instead of a rounded edge, or if the point is rough or notched. 
The length and condition of the points may be tested by holding 
the pen up to the light and bringing the nibs together slowly. 

In ease the pen becomes broken or dull from use it should be 
sharpened as follows : 

1. Provide a close grained oilstone. 

2. Close the nibs until they just touch each other. 

3. Hold the pen on the stone as in drawing a line and move 
it back and forth, revolving it slowly in the plane of motion until 



170 



MECHANICAL DRAWING 



the nibs are evenly rounded and of the same length. Fig. 175. 
This will dull the nibs. 

4. Separate the nibs and sharpen them by rubbing the outside 
on the oilstone, giving at the same time a slight rotary motion 




Fig. 175. Sharpening the Pen. Evening the Nibs 




Fig. 176. Shaepening the Pen. Grinding the Nibs 



to the handle, which is held at a small angle with the face of the 
stone. Fig. 176. The point of the pen should be examined fre- 
quently and the process continued until the nibs are sharp. If 
a burr is produced on the inside of a nib it may be removed by 
placing the inside surface flat against the oilstone and rubbing 
it lightly. 

The Compass. When using the compass for either penciling 
or inking, the legs should be adjusted so that the pen or pencil 



TRACING AND BLUEPRINTING 171 

part and the needle point are perpendicular to the drawing 
board. With the legs in this position, the compass revolves about 
the needle point as an axis and the two nibs of the pen bear 
with equal pressure, thus producing sharply defined lines. The 
compass is held by the handle, between the thumb and first finger 
of the right hand. It is rotated by rolling the handle between 
the thumb and finger. Fig. 177. If the compass is allowed to 
lean very slightly in the direction of motion, sufficient pressure 
may be put on the pen or pencil to hold it firmly in contact with 
the paper or cloth without danger of the needle point being lifted 
from the center. 




Fig. 177. Drawing a Circle with the Compass 

The pen of the compass is filled, adjusted, cleaned, and sharp- 
ened in the same manner as the ruling pen. 

The Bow Pen should be used for all circles and arcs of f 
radius or less. The pen should be filled and adjusted in the same 
manner as the ruling pen. 

Line Notation. In inking, the object lines are drawn notice- 
ably heavier than all other lines except the border line. The dif- 
ference in width produces a sharp contrast between classes of 
lines which makes the drawing easy to read and gives it a good 
appearance. In small drawings or those containing intricate 
detail the width of the object lines is slightly reduced. 

No system of line notation has ever been universally adopted. 
In this course a simple one conforming to average commercial 
drafting room practice will be used. All lines except the dotted 
line used to represent invisible edges are solid. The widths of 



172 MECHANICAL DRAWING 

lines to be used in this course are given in Fig. 178. All widths 
as indicated in Fig. 178 should be estimated by the student. As 
far as possible all lines of the same width should be drawn while 
the pen is set for that width. Before starting to ink a group of 
lines of the same width a sample line should be drawn on the edge 
of the sheet. This may be used as a guide in setting another 
instrument to give the same width of line. For instance, when 
the compass is used in drawing circles a sample of the width of 
line should be drawn to aid in estimating the setting of the ruling 
pen which will be used later. In case the pen must be reset for 
a particular line the estimated width should be determined by 
drawing lines near the sample until the proper width of line 
is secured. 



CENTEE LINE . . . , 
EXTENSION LINE i i „ 



DIMENSION LINE ...... ( ^" ^IDE" 

CEOSSHATCHING LINE.J 

FULL T^:" WIDE- 



OBJECT LINES Ij 



pOTTED -eV'WIDE-- 
BOEDEE LINE ^" WIDE— 



Fig. 178. Line Notatiox for Ink Draavings 

Order of Inking the Drawing. The drawing should be inked 
in the order given below to secure economy of time and effort. 

1. Object lines. 

a. Circles and arcs of circles. 

b. Horizontal lines (beginning at the top). 

c. Vertical lines (beginning at the left). 

d. Inclined lines. 

2. Center lines (same order as object lines). 

3. Extension and dimension lines (same order as object lines). 

4. Arrowheads. 

5. Dimension figures and notes. 

6. Crosshatching lines. 

7. Title. 

8. Border line 

In inking the title and notes, pencil guide lines on the tracing 



TRACING AND BLUEPRINTING 173 

cloth will be found of great assistance in keeping the letters 
uniform in height. In no case should letters and figures be 
penciled on the tracing cloth over those which appear on the 
pencil drawing, before they are inked. The pencil drawing 
should serve as a copy for inking figures, letters, and arrowheads 
as it does for all mechanical lines All freehand inking should 
be done with the writing pen as described under, "Preparatory 
Instruction for Lettering Plate 11," page 102. 

Erasure. On ink drawings erasures must be carefully made, 
especially if inking is to be done over the erased areas. It will 
be found that if the ruby eraser is used for removing ink lines 
the drawing surface will be left in good condition for re-inking. 
In ease a blot occurs the ink should not be allowed to soak into 
the tracing cloth. As much of the ink as possible should be 
taken up with a blotter or cloth and the remainder allowed to dry 
before erasing. The erasing shield should be used to protect the 
parts of the drawing which are not to be erased, as described on 
page 132. 

Trimming the Tracing Cloth. When the tracing is finished 
lay off one-half an inch from each corner of the border rectangle 
to make a one-half inch margin. Place the tracing on the back 
of the drawing board. With a sharp knife running along the 
edge of the T-square blade not used for riding, trim the sheet to 
the rectangle determined by the eight pencil points. In this 
process the T-square blade should be placed over the finished 
portion of the sheet. The drawing will then be held firmly and 
will be protected from the knife in case it should slip, 

DATA FOR DRAWING PLATE 19 

Given: The pencil mechanical drawing, Plate 18. 
Required: To make a tracing of Plate 18. 

Instructions: 

1. Fasten the tracing cloth over the mechanical drawing and 
prepare the surface for inking as previously described under, 
"Tracing Cloth," page 165. 

2, Ink the drawing, following the steps outlined under, 
"Order of Inking the Drawing," page 172. 



174 MECHANICAL DRAWING 

* DATA FOR LETTERING PLATE 19 

Given: Plate 19 to reduced size. Fig. 179. 
Kequired: To make the plate to an enlarged scale. 




Fig. 179. Lettering Plate 19 



DATA FOR DRAWING PLATE 20 



Given: Orthographic drawings, Figs. 182, 183, 184, and 185. 

Required: To make a pencil mechanical drawing of the 
object shown in Fig. 182, 183, 184, or 185, as assigned by the 
instructor. The views given and required may be obtained from 
the following statements. Any similar problem may be substi- 
tuted by the instructor. 

Given: Fig. 182. The front and left side views. 

Required: To draw the front and right side views. 

Given: Fig. 183. The front and left side views. 

Required : To draw the front and right side views. 

Given: Fig. 184. The front and left side views. 

Required: To draw the front and right side views. 

Given: Fig. 185. The front and left side views. 

Required : To draw the front and right side views. 



IJ 



■x; 



f 



IJOISTSH 2 XIO 



LOWER GIRTH 3-a>.e 



SILL 2-2X10 



CONCRETE FOUNDATION 




POST 3-2"X8' 



RAISED GIRTH 3-2X8 




RACE a'Ve" 



Fig. 180. Type Problem. Barn Framing. Given Views 




*3' BRACE 2V2\ 



A iJ 




BARN FRAMING 



21 I 253 1 AfiS I gCALEL-j- 



Fig. 181. Type Problem. Barn Framing. Finished Drawing 

(175) 



176 



MECHANICAL DRAWING 




m: 



Tivo scrips to co^-er tack hecta/s at A 

Fig. 182. Camp Stool 




Fig. 1&8. Step Ladder 



TRACINC} AND BLUEPRINTING 



177 





Al/ wa//s ^i "fh/ck 

Fig. 1S4. Forms for Concrete Dog Kennel 




jL 



^x4-i-Sif.hd.bolf5 

7^ 



a+^[_B-*5 



■] 



Fig. 185. Saw Buck 



178 MECHANICAL DRAWING 



DATA FOR LETTERING PLATE 20 

Given: Plate 20 to reduced size. Fig. 186, 
Required: To make the plate to an enlarged scale. 



Z2'-l|"?<19|" ROUGH ROUND RODS DRILL Z 

f 14-24 FLAT HEAD SCREWz 

Z|-ll BOLTS -6^" LONG WITH NUT AND Z 
f CHECK NUT |"-I6 ROUND HEAD BOLTZ 

zCONNECTING ROD BEARINGz 



Fig. 186. Lettering Plate 20 



DATA FOR DRAWING PLATE 21 

Given: The pencil mechanical drawing, Plate 20. 
Required: To make a tracing of Plate 20. 

Instructions: 

1. Fasten the tracing cloth over the mechanical drawing and 
prepare the surface for inking. 

2. Ink the drawing, following the steps outlined under 
"Order of Inking the Drawing," page 172. 

3. Trim the sheet and press the clotli back into the tack holes. 



TRACING AND BLUEPRINTING 
DATA FOR LETTERING PLATE 21 

Given: Plate 21 to reduced size. Fig. 187. 
Required: To make the plate to an enlarged scale. 



179 



QA;^2/ 



^^^a^^ (DiTS/ ^ 



2 FILLER PLATES ^x9"x2'-4'' REAM! 

Z PIN PLATES INSIDE {xM"x2'-6"' JIG' 



2 HINGE PLATES OUTSIDE ^xl0"x2" 



LATERAL PLATE ^x20"xr-0^ 



ALL 



HOLES ^ COUNTERSUNK ^ RIVETS 



Fig. 187. Letterixg Plate 21 




Fig. 188. Type Problem. Eesert'Oir Cap. Given Views 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 22 

Before starting to draw this plate the student should review 
the method of drawing tangent lines as described on page 147. 



TRACING AND BLUEPRINTING 



181 



DATA FOR DRAWING PLATE 22 

Given: Orthographic drawings, Figs. 190, 191, 192, and 193. 

Required: To draw the views of the object shown in Fig. 
190, 191, 192, or 193, as assigned by the instructor, from the 
following statements. Any similar problem may be substituted 
by the instructor. 







u 



Fig. 190. Book Back 



Given: Fig. 190. The front and right side views. 
Required: To draw the front and left side views. 

Given: Fig. 191. The front and left side views. 
Required: To draw the front half section and right side 
views. 

Given: Fig. 192. The front and left side views. 
Required: To draw the front half section and right side 
views. 

Given: Fig. 193. The front and left side views. 
Required: The front half section and left side views. 



182 



MECHANICAL DRAWING 




Fig. 191. Counter Shaft Pulley for 12" Wood Lathe 




J. 



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jt 



^ 



IX B 



v.y 



Fig. 192. Hand Wheel for 12" Wood Lathe 



DATA FOR LETTERING PLATE 22 

Given: Plate 22 to reduced size. Fig. 194. 
Required: To make the plate to an enlarged scale. 





Fig. 193. Leg for 12" Wood Lathe 





j2^a^22 ^^U-^/TT/ (^0-^ _ 


Z4 CHANNELS I2°xl4-8|' ROOF TRUSS" 


Zl COAT OF GRAPHITE PAINT DRILL {z 


Z12 HOLES EOUALLY SPACED TO FIT Z 


ZPiECE NO. 117 PISTON FOR 10 z 


zK p. HORIZONTAL ENGINE z 





Fig. 194. Lettering Plate 22 



(183) 



184 MECHANICAL DRAWING 



PREPARATORY INSTRUCTION FOR DRAWING PLATE 23 

Locating Points of Tangency. To secure perfect joints where 
lines are tangent in the tracings, the exact points of tangency 
should be located and marked in pencil on the tracing cloth. 
The method of locating the tangent points depends upon the geo- 




FiG. 195. Method of Locating Points of Tangency 

metrical principle that a line perpendicular to a tangent at its 
point of contact passes through the center of the circle. 

To locate a point of tangency, place the hypotenuse of either 
triangle against any edge of the other triangle, as shown in 
Fig. 195. Move both triangles as one tool until a side of the 
triangle A is coincident with the tangent line. With triangle B 
held firmly in place, slide triangle A into the position marked 
A' where the side at right angles to the tangent line passes 
through the center of the arc. A short dash should be drawn 
across the tangent line to mark the point of tangency. 

The point of tangency between two arcs may be located by 
drawing the straight line joining their centers. This line passes 
through their point of contact. Fig. 195. 



TRACING AND BLUEPRINTING 185 

DATA FOR DRAWING PLATE 23 

Given: The pencil mechanical drawing, Plate 22. 
Required: To make a tracing from Plate 22. 

Instructions: 

1. Fasten the tracing cloth and prepare it for inking. 

2. Locate the points of tangency. 

3. Ink the draAving in the usual order. 

4. Trim the sheet and press the cloth back into the tack holes. 



Z A DRAWING.' the" MECHANICAL PART" 
ZOF WHICH IS WELL EXECUTED MAY Z 
ZHAVE ITS APPEARANCE SPOILED BY Z 
ZPOOR LETTERING MAKE THE LAST Z 
Z PLATE THE BEST OF ALL^'l 2 3 4 5 6 Z 



Fig. 196. Lettering Plate 23 



DATA FOR LETTERING PLATE 23 

Given: Plate 23 to reduced size. Fig. 196. 
Required: To make the plate to an enlarged scale. 



Review Questions 



1. (a) "What is the difference between the two sides of the 
tracing cloth? (b) Which side is used in this course? 



186 



MECHANICAL DRAWING 



2. (a) Describe the process of fastening the cloth over the 
pencil drawing, (b) How is the cloth prepared for inking? 

3. Describe the process of making a blueprint from a tracing. 




Fig. 197. Governor Support 



4. (a) How is the ruling pen held for ruling lines ? (b) How 
is it adjusted to the proper width of line? (c) How is it filled? 
(d) How cleaned? 

5. (a) What precautions are taken in beginning and ending 
a line? (b) How does the pen approach and leave the paper 
in drawing dotted lines? 

6. How are the spaces between crosshatching lines estimated ? 

7. (a) Why are the needle point and the pen and pencil 
points of the compass set at right angles to the plane of the 
drawing paper? (b) How is the compass held when drawing a 
circle? (c) How is it rotated? 



TRACING AND BLUEPRINTING 



187 



8. (a) In inking, wliy are the object lines made wider than 
the other lines? (b) Give the standard width of inked object, 
extension, dimension, and center lines, and the border line. 

9. In what order are the different kinds of lines inked? 




Fig. 198. Planing Jig foe Eod Brasses 



10. (a) In what order are the object lines inked? (b) Cen- 
ter lines? (e) Extension and dimension lines? 

11. How is ink removed from a drawing ? 

12. How is the tracing trimmed to the required size? 

13. (a) Upon what geometrical principle does the method of 
finding the point of tangency between an arc and a straight line 
depend? (b) Give the steps in the construction necessary to 
locate a point of tangency. 



188 



MECHANICAL DRAWING 



DATA FOR REVIEW PROBLEMS 

Given: The top, front, and right side views of an object 
Fig. 197. 

Required: To draw the top, front half section, and right 
side views of the object shown in Fig. 197. Scale, full size. 

Given: The top, front, and right side views of an object. 
Fig. 198. 

Required: To draw the top, front, and left side views of 
the object shown in Fig. 198. Scale, half size. 




Fig. 199. Stuffing Box Gland 



Given: The top and right side views of an object. Fig. 199. 
Required: To draw the top and front half section views of 
the object shown in Fig. 199. Scale, half size. 



CHAPTER V 
ADVANCED DRAWING 

Prospectus 

The first year's work outlined in Chapters I, II, III, and IV 
are intended to give opportunity for a thorough grounding in 
the fundamentals of the theory and practice of drawing. The 
second year's work outlined in this and the succeeding chapter 
assumes a knowledge of, and skill in, the work of the preceding 
year. With this knowledge and skill as a foundation the aim of 
this chapter is to furnish applications of principles in a broader 
and more general way and to introduce various details such as 
conventional sections, screw threads, etc. 

Sheet Metal Patterns 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 24 

Development of a Surface. The student is familiar with 
many articles made of sheet metal — tin, zinc, galvanized iron, 
etc. An examination of these objects, such as pails, cups, pans, 
etc., will make it clear that some of them were made from metal 
cut from flat sheets and rolled or bent into particular forms. 
The student will recognize the geometrical solids — prism, cyl- 
inder, cone, etc., as the bases for many of these forms. For 
example, an ordinary tomato can is in the form of a cylinder. 
Before an object of this kind can be cut from a sheet of metal 
a pattern must be made which, when rolled up, will give the 
correct form. 

189 



190 



MECHANICAL DRAWING 



To construct this pattern the object is imagined rolled on a 
flat surface, such as that of the drawing board, until the entire 
surface of the solid has come in contact with the plane surface. 
Example : In Fig. 200 the prism was rolled until each of its faces 




17 b 

r 



n 



a b c cf a 



Fig. 200. Eolling a Pkism to 
Obtain the Development of Its 
Lateral Surface 



Fig. 201. Orthographic Views 
AND Development of the Lateral 
Surface of a Prism 



came into contact with the board. The prints of these faces are 
shown. If the whole figure a, b, c, d were cut out of the paper 
and folded up on the lines representing the edges of the prism 
the result would be a prism like the original. 

Fig. 201 shows two views of a square prism with the develop- 
ment of the lateral surface. It is evident from the orthographic 
views that the edges of the bases are at right angles to the lateral 
edges. When this is the case each face is a rectangle which is 
represented in the development by a rectangle equal to that of 
one side of the prism. When these rectangles are joined to- 
gether as they are when the surface is imagined unrolled, the 
edges of the bases will form straight lines. Example : Line a a. 
Fig. 201. 

The steps in the construction of the pattern are as follows : 

1. Draw two parallel lines at a distance apart equal to the 
length of the prism. It is preferable to project these lines from 
the orthographic view as in Fig. 201. 

2. Lay off with the dividers on one of these lines distances 
equal to the widths of the sides of the prism, taken in consecutive 



ADVANCED DRAWING 



191 



order, as ab, b c, c d, da. Fig. 201. For the square prism these 
distances are all equal. For a rectangular prism these distances 
would not be equal ; hence care must be taken to lay off the dis- 
tances in consecutive order 




"T 



''"1 



Fig. 202. Furnace Heat Pipe 



DATA FOR DRAWING PLATE 24 

Given: Two orthographic views of a rectangular furnace 
heat pipe. Fig. 202. 

Required: To draw a pattern, quarter size, from which 
this pipe could be made, or any similar object assigned by the 
instructor. 



Instructions: 

1. Draw the two given orthographic views. 

2. Make a construction similar to that shown in Fig. 201. In 
this case the widths of adjacent faces are not equal. The width 
of each face should be transferred to the pattern with the dividers 
from the top view starting at one comer and continuing around 
the top view until the same corner is reached. 

Beginning at this point in the course the lettering plates are 
made up of lower case letters and numerals. 



192 



MECHANICAL DRAWING 





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Fig. 203. Inclined Capital Letters 



ADVANCED DRAWING 



193 



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imii 


imm 




. . . . 

r 



STROKES 


1 


2 


3 


4 










// 








----']/r — 


'"W 


'"U 





III 

^'"fXi 
"llll"~ 


IIIH 


lllll 




i3i. 

iim 






>l 


-^~ 


4 




■Jl= 

mil 


mil 
'""rf" 

"1wi 

IIIH 


HUH 




IIIH 

Illff 






f^' 






IIIH 

"imi"~ 

"iw~ 

IHH 


IHH 

Wl 

IIHI 


"Mi 

mil 

w 


IHH 


IHH 




llH'f 







Flo. 204. IxcLixED Capital Letters 



194 MECHANICAL DRAWING 

PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 24 

The Slope of the inclined letters is equal to that of the 
hypotenuse of a right triangle, the vertical leg of which is two 
and one-half units long and the horizontal leg one unit long. 
Fig. 203. 




Fig. 205. Lettering Plate 

Lettering in Ink. The following list of plates will be made 
in ink directly on tracing cloth. A list of materials needed and 
directions for lettering in ink are given for Plate 11 of the 
vertical Gothic letters. 

DATA FOR LETTERING PLATE 24 

Given: Plate 24 to reduced size. Fig. 205. 
Bequired: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 25 

A somewhat more difficult pattern to lay out than the one just 
drawn is illustrated by a square pipe cut away at an angle to meet 
another pipe to form an elbow. Fig. 206. The edges of the lower 
base are at right angles to the vertical edges and will therefore 



ADVANCED DRAWING 



195 



unfold into a straight line. The lengths of these lines may be 
taken from the end view of the pipe and laid off on the pattern. 
It is evident in this case that not all of the vertical edges are of 








h 


b 




c 




/ 




/ 




\ 


d c 


a 















Fig. 206. Type Problem. Development of Square Pipe Cut at an Angle 

the same length. Their true lengths are shown in the front view 
and may be transferred to the pattern by drawing horizontal 
lines from it to the pattern as shown in Fig. 206. The ortho- 
graphic views, also, show that two of the edges of the slanting 
base are horizontal and the other two inclined. The lines a b, b e, 
c d, and d a are drawn, connecting points a, b, c, d, which should 
be located in consecutive order. 



^/ 








/ 


t 


^ 

\ 


y^^ 


h 


/ 
















^ 


y 


^ 








\ 


Xl^ 






'^i^' 








\ 






t^^i — 






I 


'IG. 


20 


7. 


Eectangi 


jLAR Pipe 







DATA FOE DRAWING PLATE 25 

Given: Two orthographic views of an elbow for a rec- 
tangular pipe. Fig. 207. 

Required: To draw a pattern, quarter size, from which 
the pipe could be made, or any similar object assigned by the 
instructor. 



196 MECHANICAL DRAWING 

1. Draw two given orthographic views and make a construc- 
tion similar to that shown in Fig. 206. 

PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 25 

Curved Strokes. The 6 and 9 have the same oval outline 
as the 0. This form should be kept in mind while drawing the 
6 and 9. 

Given: Plate 25 to reduced size. Fig. 208. 

Required: To make the plate to an enlarged scale. 



-000000 1470 7104 20504 = 
Z.666666 1626 6064 65276 z 

= 999999 1929 4956 9/979 z 

-I5 19I5 117 5J_7 9_ _/ = 
T 16 64 64 2 4 16 64 4 16- 16 2 - 

z 1116 4701 2196 12 4 5 7 9 Oz 



Fig. 208. Lettering Plate 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 26 

The cylinder is a very common form in sheet metal work. 
Many cans, pails, pipes, etc., are cylindrical in form. When the 
base of a cylinder is at right angles to its axis, the base will unroll 
into a straight line. Fig. 209. The length of this line must be 
found by dividing the circle representing the end view of the 
cylinder into a number of small parts and stepping off these 
lengths with the dividers on a straight line. Each distance 
transferred is the chord of the are between two points. These 
divisions must, therefore, be small enough so that the straight 



ADVANCED DRAWING 



197 



line distance between consecutive points is not greatly different 
from the distance measured between these points on the circle, 
or the arc distance. These divisions are usually made equal so 
that one setting of the dividers is sufficient for stepping off all 
the lengths. 



(cz:^ 




3 ■4. S 6 7 8 9 10 // /B f 
H — I — I — I — hH — I 1 — ! — I- 




FiG. 209. Type Pkoblem. Development of Cylindrical Surface 

Eight points equally spaced on the circumference are very 
easily obtained with the 45° triangle, or twelve points may be 
obtained with the 30°-60° triangle as shown in Fig. 210. 

Sixteen points equally spaced may be obtained by subdividing 
each of the eight divisions with the dividers. 





Fig. 210. Dividing a Circle Into 8 or 12 Parts with Triangles 



DATA FOE PLATE 26 

Given: Two orthographic views of a bench oil-waste cup. 
Fig. 211. 

Required: To draw a pattern from which the cup can be 
made, or any similar object assigned by the instructor. 

Instructions : Draw the two orthographic views and make a 
construction similar to that shown in Fig. 209. 



198 



MECHANICAL DRAWING 



PREPARATORY INSTRUCTIONS AND DATA FOR LETTERING 

PLATE 26 

The two ovals of the 8 have their major axes at 45°. The 
same combination of ovals is the basic form for the 3. 




Fig. 211. Oil Waste Cup 





_(Mz^26 (^iT^^n^ Bl7^^^ 


= 33333333 323 4353 363 = 


Z88888888 1834 687 585z. 


= ssssssssss 1473 386 83 f 


= 7 3 5 9 3 17- 
_S S S S S S Q ^ Q jQ Q^ ^ ig _ 


z 1830 1492 12345678 9- 





Fig. 212. Lettering Plate 26 



Given: Plate 26 to reduced size. Fig. 212. 
Eequired : To make the plate to an enlarged scale. 
The strokes for the S are given in Fig. 238. 



ADVANCED DRAWING 



199 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 27 

If a cylindrical object is cut away at an angle, as in the case 
of the elbow in Fig. 213, the end which is cut will not roll out 
into a straight line. The curved line into which it will unroll 
must be determined by locating a number of points through 
which it passes. This may be done by drawing lines in the 
orthographic view which represent elements or lines in the cyl- 
indrical surface parallel to the axis of the cylinder. For con- 
venience these lines should be drawn perpendicularly up from 
the points located in the base circle. The length of each of these 





Fig. 213. Development of Cylindrical Surface Cut at an Angle 



lines from the base up to the inclined line is the length of a cor- 
responding line to be located in the pattern, because it is shown 
in its true length. 

Vertical lines are drawn in the pattern from the points 
stepped off in the base. These lines represent the ones drawn 
in the surface of the cylinder. The length of these lines may 
be transferred from the orthographic view to the pattern with 
the dividers or by drawing horizontal lines across from the 
orthographic view as in Fig. 213. Example : Line a 7 in the 
orthographic view is equal to a 7 in the pattern. Here again it 
is necessary that these lengths be transferred in consecutive 
order. 



200 



MECHANICAL DRAWING 



When both ends of the cylinder are cut at an angle as in 
Fig. 214, neither end will develop into a straight line. For the 
purpose of determining the length of the pattern a line such as 
a b must be drawn in to represent an imaginary base which is at 
right angles to the axis of the cylinder. The lengths of the 
division from the circular view, A, are then stepped off on a 




Fig. 214. Type Problem. 



Developmext of Cylindrical Surface Cut at 
Both Exds 



line representing this imaginary base, c d. Fig. 214. The points 
on the curved lines in the development are located by using this 
imaginary base to measure from. If the base is centrally located 
between the two cut ends, points on both curves, on any one ele- 
ment, may be located with one measurement, as in the case shown 
in Fig. 214. 

DATA FOR DRAWING PLATE 27 

Given: Two orthographic views of the objects shown in 
Figs. 215, 216, and 217. 



ADVANCED DRAWING 



201 



Required: To draw a pattern for one of the objects shown 
in Fig. 215, 216, or 217, or any similar object as assigned by the 
instructor. 




1 


t — s . 


>■ 






— v«, 


' 




1 


'') 

" 




J 










Fig. 215. Flour Sifter 





Fig. 216. Scoop 



Instructions: Draw the orthographic views and make a con- 
struction similar to that shown in Fig. 215, 216, or 217. 



202 



MECHANICAL DRAWING 



PREPAEATOET INSTRUCTIONS AND DATA FOR LETTERING. 

PLATE 27 

Spacing of Letters. Observe carefully the spacing of the 




Fig. 217. Five Piece Elbow 




Fig. 218. Lettering Plate. 1, i, t, v, y 

letters in the words. Correct spacing is as essential as correct 
forms. 



ADVANCED DRAWING 203 

Given: Plate 27 to reduced size. Fig, 219. 
Required: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 28 

Another geometrical form commonly found in sheet metal 
work is the cone. If the cone were rolled on a flat surface its 
surface would come in contact with an area as shown in Fig. 220. 




Fig. 219. Lettering Plate 27. 1, i, t, v, y 

The vertex would remain at a fixed point. Since all straight 
lines drawn in the surface of the cone from the vertex to the base 
circle are equal in length, the base circle will unroll into an arc 
with a radius equal to the true distance from the vertex to a 
point in the base circle. Fig. 220. The length of this arc is 
equal to the circumference of the base circle of the cone and may 
be laid off by dividing the orthographic view of the base circle 
into a number of small divisions as described for the cylinder, 
page 197. These lengths are then transferred to the arc with 
the dividers. 

The pail shown in Fig. 221 is not a complete cone. It is 
therefore necessary to draw a second arc to represent the circular 
bottom of the pail. 



204 



MECHANICAL DRAWING 



DATA FOR DRAWING PLATE 28 



Given: Two orthographic views of the objects shown in 
Figs. 222 and 223. 




Fig. 220, Eolling a Cone to Obtain the Development of Its Surface 



Required : To draw a pattern for one of the objects shown 
in Fig. 222 or 223, or any similar object as assigned by the 
instructor. 

Instructions: Draw the orthographic views and make a con- 
struction for the pattern similar to that shown in Fig, 221. 



ADVANCED DRAWING 



205 




Fig. 221. Type Problem. Pail 





Fig. 222. Cream Dipper 



206 



MECHANICAL DRAWING 



DATA FOR LETTERING PLATE 28 

Given: Plate 28 to reduced size. Fig. 225. 
Bequired : To make the plate to an enlarged scale. 





Fig. 223. Funnel • 




Fig. 224. Lettering Plate, w, k, z, x, j, f 



ADVANCED DRAWING 207 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 29 

The section of a right conical surface cut at right angles to 
the axis of the cone will develop into the arc of a circle as shown 



■J(75^_ 



^w w w w w will wily wilt twit II z 
z k k k k k k kill kilty z z z z z llzz 
zx X X X X X vix xylyl viz xylyl III z 

^J J J J J J Jill Jill Jill Jill Jill Jill Ifz 
zf f f f f f fizz Jiffy fill fizz fifty z 



Fig. 225. Lettering Plate, w, k, x, j, f 

in the ease of the bottom of the pail, Fig. 221. When the conical 
surface is cut on a slant as shown in Fig. 226, the distances from 
the vertex to points on the cut are not equal and therefore the cut 
edge will not roll out into an arc of a circle. Points on the 
curved line into which this cut edge will develop may be located 
by drawing in the elements or lines in the conical surface from 
the vertex to points in the base circle. These elements may be 
located in the pattern by joining the vertex with points on the 
are of the base corresponding to the points in which these lines 
meet the base circle of the cone. 

This construction is illustrated in Fig. 227, where the points 
in which the elements pass through the cut edge of the cone are 
located in the development by finding their true distances on the 
elements from the vertex (see horizontal lines in front view) and 
transferring these lengths to the corresponding lines in the devel- 
opment. This may be done with the dividers or by swinging 
arcs with the compass as shown in the figure. 



208 



MECHANICAL DRAWING 



The true lengths of the contour elements of the cone are 
shown in the front view, Fig. 227, in o e and o d. None of the 




iSlill /O 9 6 7 6 S 4- 3 SI 

Fig. 226 Development of a Cone Cut at an Angle to Its Axis 

other elements show in their true length, although they are known 
to be equal in length to o e and o d. 



ADVANCED DRAWING 



209 



In order to find the distance from the vertex to a point such 
as a on an element a construction is necessary. The student 
should try to fix in mind the principle on which this construction 
is made^ which is as follows. Since any element o c is equal in 
length to d it may be imagined turned around into coincidence 
with o d by keeping the end e always in the base circle. Thus the 



o 
/ ' ^ \ 

\ \^ 

^ . — ^ 



(^ 







\ 




- 



\ 




) 


/ 


\ 


\ 


e 




c a 



Fig. 227. Illustrating Method of Obtaining True Lengths of Elements 

point e moves through an are e d. The point at the other end of 
the line o e remains fixed, but any point, such as a between o 
and e will move on an arc ab. Thus when oc is brought into 
coincidence with o d the true length of o e is shown in o d and the 
true length of any part of it, such as o a, is shown in o b. Notice 
that the base circle of the cone appears as a straight horizontal 
line e d, Fig. 227, and also that the are a b appears as a straight 
horizontal line in the front view of the cone. With this point 
clearly in mind it will be evident that to find the length of o a it 
is only necessary to draw the horizontal line ah as construction. 

DATA FOR DRAWING PLATE 29 

Given: The orthographic views of the objects shown in 
Figs. 228 and 229. 



210 



MECHANICAL DEAWING 



Required : To draw a pattern for one of the objects shown 
in Fig. 228 or 229, or any similar object assigned by the 
instructor. 

Instructions: Draw the orthographic views and make a con- 
struction for the pattern similar to that shown in Fig. 226. 





Fig. 228. Ventilator Pipe 




Fig. 229. Scale Scoop 



DATA FOR LETTERING PLATE 29 

Given: Plate 29 to reduced size. Fig. 231. 
Eequired: To make the plate to an enlarged scale. 



ADVANCED DRAWING 



211 





" 


STROKES 1 




1 


2 


3 












"r'T 








A 


=r- 






-.{ ■ 








::::.7 


■#/f1 






Jl 










i/c: 


~\ 






=n 












T 


m- 


77f 

















Fig. 230. Lettering Plate, r, h, n, m 



r r r r r r r kirk vitrify kirts six z 
in In In In In In hilt whirl whist his z 
n n n n n n hint lynx hint lynx z 
m m m m mink hymn milk hint z 



z.V—23'-9^ 



7" 



65'-4f—\ 



Fig. 231. Lettering Plate 29. r, h, n, m 



212 



MECHANICAL DRAWING 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 30 

If a pyramid were rolled on a flat surface its faces would 
come iu contact with triangular areas such as shown for the 
square pyramid in Fig. 232. In this case there are four triangles. 
For a hexagonal pyramid there would be six triangles, etc. The 
length of the edges of the pyramid from the vertex to the corner 
of the base are all equal. Therefore if an arc of radius equal to 
their length were drawn these lines would all end in the arc. The 
sides of the base of the pyramid will appear in the pattern as 





Fig. 232. Eolling a Pyramid to 
Obtain the Development of Its 
Lateral Surface 



Fig. 233. Type Problem. Devel- 
opment OF A Square Pyramid 



chords of this arc. In the case of the square pyramid as shown 
in Fig. 233, none of the edges from the vertex to the base are 
shown in their true length. A construction such as that described 
for finding the lengths of the elements of the cone must be made 
for finding the lengths of these edges. Referring to 'Fig. 233, 
the base of the pyramid is inscribed in a circle which corresponds 
to the base circle of the cone. If the edge oc, for example, is 
imagined turned as was the element of the cone, into a position 
corresponding to the contour element of the cone, it will show 
in its true length in the front view. o. d, Fig. 233, therefore 
represents the true length of the edge o c. With this length as a 
radius, an arc may be drawn and the points representing the 
lower corners of the pyramid may be located on it by stepping 
off lengths equal to the side of the base, such as e c. 



ADVANCED DRAWING 



213 



DATA FOE DRAWING PLATE 30 

Given: The orthographic views of the object shown in 
Fig. 234. 



5; 


"K 


7^ 


7 




/ 


y 


^ 


\ 




Y- 


■/^■^ 








"t 


\ 


\ 


\'- 




- 


CI 








Fig. 234. End for Grain Conveyor, 




Fig. 235. Lettering Plate, u, o, c, e 



214 MECHANICAL DRAWING 

Required: To draw a pattern for the object shown in Fig. 
234 or any similar object as assigned by the instructor. 

Instructions : Draw the orthographic views and make a con- 
struction for the pattern similar to that shown in Fig. 233. 



1 


_(?Ja^dO 


(Ja^^^£)azi_ 


zu u u u u u u 


hum tumult funny z 


ZLO O O 


moon form fourtli z 


Z.C c c c c c c 


lock column corks z 


z.e e e e e e e 


clever come fewer z 


z 66f ^O'-Of I3~ 997'-6"z 





Fig. 236. Lettering Plate 30. u, o, c, e 

PREPARATORY INSTRUCTIONS AND DATA FOR LETTERING 

PLATE 30 

Curved Strokes. The major axes of the oval letters of this 
plate are in the direction of the slope. 

Given: Plate 30 to reduced size. Fig, 236. 
Required: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 31 

The true length of the edge of a pyramid cut at a slant is 
found as previously described. Finding the true length of the 
edges from the vertex to the point where the edge strikes the cut 
involves the same theory discussed in connection with the pattern 
for the cone, page 209, Fig. 227. The construction is also the 
same. 



ADVANCED DRAWING 



215 



DATA FOR DRAWING PLATE 31 

A problem for this plate may be supplied by the instructor 
if desired. 





Fig. 237. Development of Pyramid Cut at an Angle to Its Axis 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 31 

Curved Strokes. The major axes of the ovals of this plate 
make 45° with the horizontal. 



DATA FOR LETTERING PLATE 31 

Given: Plate 31 to reduced size. Fig. 239. 
Required: To make the plate to an enlarged scale. 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 32 

Intersection of Surfaces. The objects thus far considered 
have been of the form of geometrical solids. There is another 
class of patterns which involves the laying out of the line where 



216 



MECHANICAL DRAWING 




Fig. 238. Lettering Plate, a, d, q, g, b, p, s 




Fig. 239, Lettering Plate 31. a, d, q, g, b, p, s 

the surfaces of two solids meet or intersect. An example of the 
intersection of two prisms is afforded in the case of the roof of 



ADVANCED DRAWING 



217 



a house, as shown in Fig. 240. The line of intersection is the line 
abc where the roofs meet. It is quite evident that this broken 
line abc lies in the surface of the main roof and also in the sur- 
face of the dormer roof, or, in other words, it is a broken line 
which is common to both roofs. This illustrates the general defi- 
nition of a line of intersection, which is as follows : The line of 




Fig. 240. Illustration of an Intersection 



intersection "between two surfaces is the line which lies in both 
surfaces. In the following discussion of the laying out of pat- 
terns of objects containing intersecting surfaces, this definition, 
if kept clearly in mind, will help in grasping the principles on 
which the methods are based. 

In Fig. 241 is shown the orthographic view of a cylinder inter- 
secting a square prism. In this case the right side view is unnec- 
essary for the purpose of laying out a pattern. It is drawn to 
show the method of constructing the line of intersection in this 
view, as in some cases it will be necessary to draw a view corre- 
sponding to this one. It also gives a better idea of the method 
by which the points on the line of intersection are located for 
transferring to the pattern. 

Development of the Cylindrical Snrface. As in Plate 26, the 
edge of the upper base of the cylinder which is at right angles 
to the axis of the cylinder will develop into a straight line. The 
length of this line may be determined, as before, by dividing the 



218 



MECHANICAL DRAWING 



base circle into a number of equal small divisions and stepping 
them off with the dividers. To obtain the development of the line 
of intersection, elements are drawn in the surface of the cylinder, 
preferably from the points already located in the base circle. 
Lines are then drawn in the patterns to represent them. Their 
lengths may be transferred from the orthographic views by means 




Fig. 241. Type Problem. 



Intersection of a Square Prism and a 
Cylinder 



of the dividers or projected by horizontal lines as shown in 
Fig. 241. 

The pattern for the entire surface of the prism is laid out as 
m Plate 24. The hole opening into the cylinder or the line of 
intersection is determined in the pattern as follows : In the front 
view the lateral surfaces of the prism are seen edgewise, and con- 
sequently the points in which the cylinder strikes the surfaces 
of the prism are seen in the points where the lines representing 
these elements cross the lines representing the surfaces of the 
prism. Example : b is the point in which the element a b of the 



ADVANCED DRAWING 



219 



cylinder strikes the surface of the prism. If a line is drawn in 
the surface of the prism through point b and parallel to the 
lateral edges of the prism, the distance of this line from the edge 
of the prism may be located on the pattern. The true 





Fig. 242. EooF Cap and Ventilator 




E 



Fig. 243. Soldering Stove 

length of this line, which is shown in the top view, may 
be transferred to the pattern with the dividers or projected from 
the orthographic view as indicated in the drawing. A similar 
construction should be made for the other points on the line of 
intersection. 

DATA FOR DRAWING PLATE 32 

Given: The orthographic views of the objects shown in 
Figs. 242 and 243. 



220 MECHANICAL DRAWING 

Required: To draw the orthographic views and construct 

patterns for the object shown in Fig. 242 or 243, or any similar 
object as assigned by the instructor. 



PREPARATORY INSTRUCTIONS FOR LETTERING PLATE 32 

Composition. In the following composition plates the spacing 
of letters and words should be given as much consideration as the 
forms of the letters. The student should strive to produce a good 
general effect in the plate 



Drill ^ Ream I" Bore 2" Holes z 
to Suit Motor Used End of studz 
to be fluttened and cast In partz. 
I. Use Fillers 513 to Allow All z 
Gears to Mesh Properly Head z 



Fig. 244. Lettering Plate 32 



DATA FOR LETTERING PLATE 32 

Given: Plate 32 to reduced size. Fig. 244. 
Required: To make the plate to an enlarged scale. 



PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 33 

The laying out of patterns for the surfaces of two intersecting 
cylinders involves the same general principles as described for 



ADVANCED DRAWING 



221 



the intersection of the prism and cylinder in Plate 32. The base 
of the smaller of the two cylinders should be divided into a num- 
ber of equal parts and its surface developed as before. 

The entire surface of the larger cylinder is laid out and the 
points in which the elements of the smaller cylinder strike the 




Fig. 245. Type Problem. Intersection of Two Cylinders 

surface are located by drawing elements of the larger cylinder 
through these points. The spacing of these elements is obtained 
by stepping off the arcs ab, b c, etc., Fig. 245, between the points 
representing these elements in the end view (top view in this 
case) of the cylinder. 



DATA FOE DRAWING PLATE 33 

Given: The orthographic views of the objects shown in 
Figs. 246 and 247. 

Required: To draw the orthographic views and construct 
patterns for the objects shown in Fig. 246 or 247, or any similar 
object assigned by the instructor 



222 



MECHANICAL DRAWING 





Fig. 246. Eave Trough and Down Spout 




Fig. 247. Furnace Smoke Pipe 



DATA FOR LETTERING PLATE 33 

Given: Plate 33 to reduced size. Fig. 248. 
Required: To make the plate to an enlarged scale. 



ADVANCED DEAWING 223 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 34 

In the preceding plates, elements were first drawn in the cylin- 
der to strike the surface of the other solid. In the construction 
of the intersection line between a cylinder and cone, example, 
Fig. 249, elements of the cone are first drawn striking the surface 
of the cylinder. This is made necessary by the fact that the cone 
has a slanting surface which is not seen edgewise in any view, 
consequently it is impossible to tell where elements drawn in the 
surface of the cylinder strike the surface of the cone. 



t2-l^^ 19^" Rough Round Rods z 
= /-// Bolts- 6^' Long Without z 
z/Vut &. Check Nut Connecting z 
z Rod Bearing 14 - 24 Flat Headz 
z Machine Screw Graphite Paint z 



Fig. 248, Lettering Plate 33 

The elements of the cone should first be drawn in the front 
view and in such a manner as to divide the circular base of the 
cylinder into a number of small parts. It is evident that these 
parts cannot all be equal as in the preceding problems. 

Draw the top views of these same elements of the cone. This 
is doue for element ab by projecting from a to the base circle of 
the cone in the top view to determine the foot of the element a b 
in the top view, and connecting this point with the apex. 

Elements should now be drawn in the surface of the cylinder 
to pass through the points in which the elements of the cone strike 
the surface of the cylinder. Example : c in the top view is 
projected from the point c in the front view. 



004. 



MECHANICAL DRAWING 



The other points on the intersection are located in the top 
view in the same manner. 




PH 



The surface of the cylinder may now be developed following 
the usual method. Attention is again called to the fact that the 
elements of the cylindrical surface are not equally spaced. It 



ADVANCED DRAWING 



225 



will therefore be necessary to step off each division separately, 
taking care to place them in consecutive order in the pattern. 
The true lengths of the elements from the base to the line of inter- 
section are shown in the top view and may be either transferred 
to the pattern with the dividers or projected from the top view 
as shown in Fig. 249, 





Fig. 250. Oil Eeceptacle 



The entire surface of the arc is laid out in the pattern by 
striking an arc of radius equal to the length of the elements of 
the cone and stepping off on this arc a distance equal to the cir- 
cumference of the base circle. On this arc are located the feet 
of the elements on which points on the intersection were found, 
by transferring the distances between the feet of these elements 
from the top view of the base circle. The points on the line of 
intersection are located on these elements by finding the true 
lengths from the vertex of the cone to the line of intersection for 
each element. The construction for this is described in detail on 
page 209. 

DATA FOR DRAWING PLATE 34 

Given: The orthographic views of the objects shown in 
Fisrs. 250 and 251. 



226 



MECHANICAL DRAWING 



Required: To draw the orthographic views and make a 
construction for the pattern of the objects shown in Fig. 250, 
251, or any similar object as assigned by the instructor. 

Instructions: The fact that the cylinder in Fig. 250 is larger 
in proportion to the cone than in the type problem makes no dif- 
ference in the principle of the problem or the method used in its 
solution. It is only necessary to assume a base for the cone and a 
vertex as indicated by the dotted lines. 





Fig. 251. Exhaust Head 



In the object shown in Fig. 251, the axis of the cylinder is 
parallel to the axis of the cone. The elements of the cone should 
always be drawn first in the view in which the cylindrical surface 
shows as a circle, which, in this case is the top view. 



DATA FOR LETTERING PLATE 34 

Given: Plate 34 to reduced size. Fig. 252. 
Required: To make the plate to an enlarged scale. 

A Bill of Stock is a tabulated form, such as the bill of mate- 
rial, but which gives the rough and sometimes the finished sizes 
for each different piece of timber and the number of each size 
required, together with a list of all other materials to be used in 
the project. Such a tabulated summary makes it possible to cut 



ADVANCED DRAWING 227 

all stock and to calculate the cost of all materials for any project 
in wood. Example : Fig. 267 shows a bill of stock for a table. 

Sectional Views, Very often a drawing is not clear because 
the interior of the object is complex or because a part of it is 
obscured by other lines. In such cases the object may be repre- 



J4 (^oA^Daz^^ 

ZL I" Drill and Ream Holes for All z. 
z. Pieces. Spring Must Deflect 2" z 
z Factor of Safety 1. 5 Patterns z 
z l§" Core for Piece No 640139 z 

o" 

z ^ Chain (277 Links) Material z 



Fig. 252. Lettering Plate 34 

sented more clearly if a portion of it is imagined cut away to 
expose the hidden part. The most common examples of this 
method of representation are: (1) half-section in which the 
object is cut into two similar parts through an axis of symmetry, 
and (2) quarter-section in which the Object is cut in to the center 
on two planes at right angles. These sections are described in 
detail on pages 98 and 99 and illustrated on page 94, 

Other methods of sectioning may be used, depending upon the 
form of the object or part which it is desired to make clear. Fig. 
253 illustrates a case where the section is taken on a broken line, 
A B. In drawing the section view, the cut surface A is con- 
sidered revolved into the same plane with B. Fig. 254 illus- 
trates what is called a partial section. The ragged line indicates 
that a part of the shaft has been broken away. 

The cross-section of an object is often given by showing a 



228 



MECHANICAL DRAWING 



revolved section in one of the views, Fig. 255 or 265. Where the 
section cannot well be revolved a line may be drawn across the 
view of the part at the place where the section is taken and the 




Section on AOB 

Fig. 253. Broken Line Section 




Fig. 254. Partial Section 



section drawn in an open space near the view. Reference should 
be made to the line on which the section is taken. Fig. 256. Such 
parts as spokes or arms of wheels, solid shafts or rods, screws, 
bolts, studs, and nuts are not represented as cut when the section 
plane passes through their axes. Fig. 257. Ribs and webs are 



ADVANCED DRAWING 



229 



not sectioned when the section plane is parallel to their lateral 
faces. 

When a section is taken through an assembly, adjacent parts 
are crosshatched in different directions to aid in distinguishing 
one from another. 




Fig. 255. Revolved Section 

Various combinations of lines are used to represent sections of 
different materials. No standard section notation has ever been 
universally adopted. It is customary to add a note giving the 




Section A A 



Section BB 



Fig. 256, Removed Sections 



name of the material unless a local section notation is in use. 
Except for a few cases where it is desirable to distinguish between 
the metals in adjacent parts, such as the babbit and the casting 
of a bearing, nothing is gained by using characteristic section 
lines since, in general, a note must be added to insure proper 
interpretation. Fig. 258 shows a few sections in common use. 

Breaks. Where it is desirable to omit part of a shaft or rod, 
either may be broken and the break indicated as shown in Fig. 



230 



MECHANICAL DRAWING 




Fig. 257. Section Through Eibs, Shafts, Bolts, etc. 







CAST IRON CAST STEEL WROUGHT IRON BRASS 




>6<VxVxxVx 





COPPER 



WIRES 



INSULATION 



^m 



z 



^m 



^ 



BRICK 



•.■.■?-..-?=-c-v„. 
•>:5.-.vVCi-<?^.?.r- 

■■".•••i^'.n??.'-.-.-!!' 



CONCRETE 





WOOD 



Fig. 258. CoNvENTiONjiL Cross-Sectioning 



ADVANCED DRAWING 



231 



259. The ragged line representing the break is drawn freehand 
in both the pencil and the ink drawing. 



ffectan^u/ar Bar 



ffecfangu/ar 5ecf'on -iViPOi^ 



VfJfJffffJJffffff>fJT 



Found ffod 



Fi^e or HoZ/oiY Shaft 



I B.eam 



Charjne/ An^/e 

Fig. 259. Conventional Breaks 



Z-Bar 



Wood Screws are made of steel or brass. They have heads of 
various shapes as shown in Fig. 260. The size of screws is given 
in terms of their number and their length, which is indicated by 
giving the gage number. The threads of wood screws are repre- 
sented conventionally as shown in Fig. 260. 

Furniture and Cabinet Details. Various joints and a few 
other common constructions used in furniture and cabinet con- 
struction are shown in Figs. 261 and 262. 



<«QXClO 



Fig. 260. Conventional Representation of Wood Screws 



Furniture and Cabinet Problems 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 35 

The problems for this plate were selected with the idea of 
giving practice in drawing and dimensioning projects in furni- 
ture making and also to set before the student typical examples 



232 



MECHANICAL DRAWING 



r^ 




1 






? 





6/i/ec/ ancf 0/ocked 
Fig. 261. Joints 




d 




Spfine Joirrf- 



Oai^o and ffatbet 



rJ \ 











f^ZZJ 



Da^o, Ton^i/e^ancf /Tabbef 



1=1 



a 



/iaunchec/ Mi7rf-/5e and Tenon 



Lap Poh'eta// 
Fig. 262. Joints 



^ 



(233) 




~ tJ 



1^ — 



.-^ ^%~ 



J 




it^] 






X 

o 

z: 
bj 

CO 
i^ 

a: 
o 



-Hf/ 



i_ 

T" 





fr-Hri 






-.1 



.ILL 



14 



"'1 

^1 



■i*- 



^■1 5 



- p/ *\^ 



4= 



— -.s-.s ■ 



i^' 



^ 



kf 



^ 






T 








b 




II 




-ini 


UJ 




_J 


1 


CQ 


-J 


< 


< 


f- 


UJ 


)^ 


< 


(0 


-3 


UJ 





Q 




o 




vO 




<0 







33 



=iJ. 



r^TT 






^D rawer" 5 u/c/e, 

;"L, •Section on MN 




(236) 



Fig. 265. Machine Shop Bench 



ADVANCED DRAWING 



>37 




'Dsfzzi/of Joinr at < 



Fig. 266. Phone Table and Chair 



238 



MECHANICAL DRAWING 



BILL OF 5T0CH 


PC5 


rstZE 


NAME 


MATERIAL 


NO FT. 


PtR.n 


TOTAL 


1 


I"X 30X4a" 


TOP 


OAK 


10 


^.\Z 


^Teo" 


:2. 


fx5|T4l|' 


RAILS 


.1 


3.5 


' '1 


kz 


2 


|"x5^"xE5| 


■' 


.1 


2.16 




,26 


2 


f'n 3"X£S^" 


.. 




i;o3 


.. 


,13 


4 


g"x2"xl6|" 


SLATS 




,94 




.11 


2 


^X4X16| 


.1 


.. 


■S4 


" 


.11 


1 


|'xia"x4;|" 


BOTTOM 


" 


3.5 


.. 


AZ 


4 


zgkEgxao" 


LEGS 


" 


5.E 


,. 


.62 


3 


g"x4"x£5" 


DRAWER 




2.08 




.2B 


1 


j"X4"xa4" 


" 


.. 


£7 


^^ 


.06 


1 


I'x 23^X25" 


DRAW. BOT 


PINE 


4.80 


^45 


;is 


2 


("j(£"X£5" 


DfTAVV. GUIDE 


OAK 


.69 


.12 


i08 .. 


TOTAL COST 


aise- 




c:oic33 



^3 ■^,■3" 

<»)i<n -.jp X g 

Detai/ of Draiver 




Fig. 267. Library Table 



ADVANCED DRAWING 



239 



of furniture construction. In ordei to cover this field as thor- 
oughly as possible, two type problems of widely different char- 
acter are presented. Figs. 263 and 264. The student should fix 



Ct-ossbar 



^ ^ Woade» P/n 




1% i_ 

Z/o/'nf and Cornef af Q 



Fig. 268. Morris Chair 



in mind the correct proportion of the joints used in these prob- 
lems as well as their names and uses by referring to the discussion 
aiui figures on pages 231, 232, and 233. 



240 MECHANICAL DRAWING 

DATA FOR DRAWING PLATE 35 

Given: The perspective sketch of the object shown in Fig. 
265, 266, 267, or 268. 

Required: To draw the orthographic views of the object 
shown in Fig. 265, 266, 267, or 268, or any similar problem as 
assigned by the instructor. 



-3" - 

z Or 00 ve q^ R in finished face. z 

zDrill for ~ Split Coffer 1914- I5z 

z All Fillets Q R Unless Otherwisez 

z Specified. Key for 9" Spur Gearz 

z l£x6^" Stud Bolt Nut, 1915 -i6z 



Fig. 269. Lettering Plate 35 

The problems for this plate are designed to give practice in 
making working drawings for various kinds of cabinet work and 
to familiarize the student with typical cabinet construction. 

DATA FOR LETTERING PLATE 35 

Given: Plate 35 to reduced size. Fig. 269. 
Eequired: To make the plate to an enlarged scale. 

DATA FOR DRAWING PLATE 36 

Given: The pencil mechanical drawing, Plate 35. 
Eequired: To make a tracing of Plate 35. 



ADVANCED DRAWING 241 

DATA FOR LETTERING PLATE 36 

Given: Plate 36 to reduced size. Fig. 270. 
Required: To make the plate to an enlarged scale. 



Make Oil Tight Drill for No, 161 
Standard Flat Head Machine : 
Screw. v3p Lock Nut Washer : 
These Holes in Piece No 641811 
Only Drav/ing No. 166, Piece : 



Fig. 270. Lettering Plate 36 



DATA FOR DRAWING PLATE 37 

Given: The orthographic views of the objects shown in 
Fig. 273, 274, 275, or 276. 

Required: To draw to large scale two views of objects 
shown in Fig. 273, 274, 275, or 276, with sections and details of 
joints and paneling; or any similar problem assigned by the 
instructor. 



.> 


'i 






':i^ 








KS'> 


c^ 












n.. 




^ -r^- ■ - ■ ■■ 




^ 




s- 






"^ ..e^ > * 


J 
























































1 


lu 










Lj 


D 


^ 









o 
o 

o : 
(T o X. 

^ o 
o : 
o 

-J Q 

o 
o 



■ I 

I 




244 



MECHANICAL DRAWING 




Fig. 273. Glue Bench 




Fig. 274. Cabinet for Drawing Eoom 



|:r_-=; 




//: 



6hss 2^fx/-6 

''i 



■i-si- 



'4 // 



& 



ff 









W/ 



■/-Sz 






jlL 



"•"^^ 






^ 






<-*\ 



Fig. 275. Cabinet for Clothes Press 



+ + 



+ >,., -u> ^ 



=W^ 






+ 



+ 



■ B-/I- 



5j_ 



S3" 









U — i 



"^^ 



31 






lJ_L 



Fig. 276. Chiffonieb 



(245) 



246 MECHANICAL DRAWING 



DATA FOE LETTERING PLATE 37 

Given: Plate 37 to reduced size. Fig. 277. 
Required: To make the plate to an enlarged scale. 



z. Round Point Set Screw -Brass^ 
z/ Required. Tap 2^ Special z 
Z/?(9 Threads per I' Bottom z 
z Spring Plate Brass -Pint sin -/ z 
z. Required. Outside Pin is In All OverzL 



Fig. 277. Lettering Plate 37 



DATA FOR DRAWING PLATE 38 

Given : The pencil mechanical drawing for Plate 37. 
Required: To make a tracing of Plate 37. 



DATA FOR LETTERING PLATE 38 

Given : Plate 38 to reduced size. Fig. 278. 
Required: To make the plate to an enlarged scale. 



ADVANCED DRAWING 247 



MACHINE DRAWING 

A Bill of Material may be given on the drawing or on a sep- 
arate sheet. It is a tabulated form in which such information as 
the following is given : 

1. Number of each part required on one complete machine 
or structure. 



: A careful study of the form z 
.and proportion of each letter z 
.must be made before the stu- z 
dent can hope to make any cons 
siderable progress in lettering z 



Fig. 278. Lettering Plate 38 

2. Description or name of piece. 

3. Mark or number by which a piece is designated on the 
drawing. 

4. General drawing number. 

5. Shop drawing number. 

6. Erection drawing number. 

7. Material from' which each piece is made, 

8. Pattern number if cast. 

9. Where used. 

10. Estimated weight. 

11. Order number. 



248 



MECHANICAL DRAWING 





l" 


3i 


f" 


> 

< -3" > 


^ T? 


4 


'-4 ^ 


4 


^^4 ^ 


•0,5514-^ 


ir 


5wm^Arm 


-i- 


—frrt. — 




5 


ShieU P/afe 


1 


w:/. 




4 


Feed Leyer Latch Pin 


/ 


WJ, 




3 


Reach Poc^ 


/ 


W.l. 




2 


Thumb Latch 


1 


C.I. 




1 


Fee of Letter 


/ 


C.l. 




DETAILS 

FOR 
OHIO MONARCH SHREDDER 




34- 359 A.G.S. SCALE-HALF SIZE 



Fig, 279. Bill of Material 




Fig. 280. Construction of the Helix 



The bill of material includes standard parts such as bolts and 
screws which are not detailed on the drawings. A simple bill of 
material is shown in Fig. 279. 



ADVANCED DRAWING 



249 



Screw Threads. The curve of the screw thread is the helix. 
It is generated by a point which moves on the surface of a cylin- 
der and which advances uniformly in the direction of the axis of 
the cylinder and at the same time has a uniform motion around 




^P^ 



^lh 




U S. STANDARD 




N^ ^^ -y /a/ f^rji "per incft of /en^ffr i 




CoTiplete threads -F/at tops —Sharp boffoms 



BRieOS STANDARD P1P£ Taf?EADS-MODlFlED 

Fig. 281. Proportion of Common Thread Forms 



its axis. Fig. 280 shows the construction for the helix. The dis- 
tance in the direction of the axis traversed by a point in one revo- 
lution is called the 'pitch. Pitch in the case of a thread is its 
advance in the direction of the axis in one revolution. 

In Fig. 281 the proportions of the several common thread 
forms are shown to a large scale. 



250 



MECHANICAL DRAWING 



The V-thread is shown in Fig, 282 as it would actually appear 
with the edges drawn as helices. On account of the difficulty of 
constructing and drawing these curves they are usually conven- 






FiG. 282. V-Thread, Showing Helices 



tionalized into straight lines as shown in Fig. 283. The method 
commonly used for representing screws up to about one inch in 
diameter, as measured on the drawing, is still further simplified 
by omitting the short inclined lines forming the "saw teeth." 



ADVANCED DRAWING 



251 



Fig. 284. On the pencil drawing no distinction is made in the 
weight of the two sets of parallel lines drawn across the screw, 
but on the tracing it is customary to make a striking contrast 
between the longer and shorter lines as shown. 




Fig. 283. V-Thread. Conventional Eepeesentation for Large Sizes 



In this course the shorter lines will be made object-line width 
and the longer lines center-line width. The angle at which these 
lines are drawn is estimated. It remains practically constant for 
all sizes of standard screws as the pitch of the thread increases 
with the diameter of the screw. It will be noted that the lines in 
the section view of the nut make the opposite angle to the hori- 
zontal that those on the screw make because of the fact that the 



252 



MECHANICAL DRAWING 



part of the nut shown matches the invisible half of the screw. The 
lines are usually spaced by eye. Guide lines should be drawn to 
limit the length of the shorter lines. 

In the conventional end view of the bolt, the circle represent- 
ing the outer edges of the thread is a full line, while one-half of 
the circle representing the inner edges of the thread is a dotted 
line and the other half is a full line. 




FiQ. 284. V-Thkead. Conventional Eepresentation for Small Sizes 



In the conventional end view of the nut, the circle represent- 
ing the inner edges of thread is a full line, while one-half of the 
circle representing the outer edges of the thread is a dotted line 
and the other half is a full line. 

A study of the relation of these conventions to the form of 
the object should enable the student to fix in mind the principles 
on which they are based. With this relation in mind it will be 
unnecessary for him to refer to the figures in rendering the 
convention. 

The United States Standard (U. S. S.) or Sellers thread, 
Fig. 281, differs from the sharp V-thread in that the outer and 
inner edges of the thread are flattened. The same convention 
is used for representing it that is used for the sharp V-thread. 



ADVANCED DRAWING 



253 



The Square Thread is shown in Fig. 285 with the edges drawn 
as helices. Fig. 286 is a conventional representation of the screw 
and nut in which the helices have been replaced by straight lines. 




Fig. 285. Square Thread. Edges Drawn as Helices 



For small sizes, the method shown in Fig. 287 is generally 
used because of its simplicity. The Acme screw thread is rep- 
resented conventionally as shown in Fig. 288. It is convenient 
in drawing to make the angle between the faces of the thread 
30° instead of 29°. 




Fig. 286. Square Thread. Conventional Representation for Large 

Sizes 





Fig. 287. Square Thread. Conven- 
tional Representation for Small Sizes 

(254) 



Fig. 288. Acme Thread. Con- 
ventional Representation 



ADVANCED DRAWING 



255 



Pipe Thread. The basic form of the Briggs standard pipe 
thread is that of the V-thread. This thread is rounded slightly 
.at the outer and inner edges. A modified form m which the 
threads have flat outer edges and sharp inner edges is shown in 
Fig. 289. This form is used by manufacturers because of the 
comparative ease with which taps and dies are made for cutting 
the threads. 




Fig. 289. Pipe Threads. Conventional Representation 



The threaded portion of the pipe tapers one thirty-second 
of an inch in radius for each inch of length. 

Pipe threads are represented conventionally as shown in 
Fig. 289. 

Springs. The curve of the coil spring is the helix. Fig. 290 
shows a spring in which the curves are drawn and also the 
conventional representation which shows the curves replaced by 
straight lines. 

Bolts and Nvts. A bolt consists of a rod with a head on one 
end and a screw on the other to receive a nut. Fig. 291. What 
are known as United States Standard bolts and nuts are shown 



256 



MECHANICAL DRAWING 



in Figs. 292 and 294. The proportions given by the formulae are 
those adopted for rough bolts and nuts. The finished nuts are 
3^" less in width and thickness than the rough nuts. The fin- 




FiG. 290. Coil Spring Showing Actual and Conventional 
Eepeesentation 




BOUT CAP SCREW STUD STUD BOLT 

Fig. 291. Common Screw Fastenings 



ished heads have the same sizes as the finished nuts. A table of 
standard sizes may be found in an engineering handbook. 
United States Standard threads are used on these bolts. 





Fig. 292. Actual Proportions. 
Hexagonal Head — U. S. Standard 
Bolts and Nuts 



Fig. 293. Conventional Repre- 
sentation. Hexagonal Head — U. 
S, Standard Bolts and Nuts 





Fig. 294. Actual Proportions. Fig. 295. Conventional Eepre- 

Square Head — U. S. Standard sentation. Square Head — TJ. S. 

Bolts and Nuts Standard Bolts and Nuts 

(257) 



258 MECHANICAL DRAWING 

Figs. 293 and 295 show the conventional methods of repre- 
senting hexagonal and square bolt heads and nuts. Hexagonal 
heads and nuts are usually drawn to show three faces, whereas 
square heads and nuts are drawn to show two faces. When this 
is done the hexagonal forms are easily distinguished from the 
square forms. 

Since the proportions of the head and nut of standard bolts 
are fixed, it is only necessary to give three dimensions, viz., the 
length of the bolt under the head, the length of the threaded 
portion, and the diameter. 

A Stud is a rod threaded at both ends. One end is screwed 
into a threaded hole. The other end receives a nut. In Fig. 291 
a standard nut is used. 

A stud placed through two unthreaded holes with a nut at 
each end is called a stud holt. Fig. 291. 

Cap Screws are similar in form to bolts. They hold two 
parts together by passing through an unthreaded hole in one 
and a threaded hole in the other. Fig. 291. Heads of various 
forms are used as shown in Fig. 296. 

Machine Screws are similar to cap screws in form. They 
differ from them by being measured in decimals instead of even 
. fractions of an inch. 

Tap Bolts have the same form as cap screws except that they 
are not finished before threading, are threaded for their full 
length, and are used for rough work. 

Set Screws are used ordinarily to prevent relative motion of 
two parts such as a pulley and shaft. The screw is passed 
through a threaded hole in one part and the point is forced 
against another part. The proportions of the set screws and the 
shapes of the different points are shown in Fig. 297. 

Multiple Threads. It is sometimes necessary to increase the 
distance traversed by a nut in one revolution. If a coarse 
enough single thread is used to give the advance required, the 
strength of the bolt may be considerably diminished. To obviate 
this difficulty, more than one thread may be cut side by side. 
The advance for one revolution of a multiple thread is commonly 
called the "lead," and the pitch is the distance between corre- 
sponding points on two successive threads. Fig. 298. The con- 




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SQUARE 



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> — 'fW 

FLAT FILLISTER OVAU FILL15TER 




FLAT COUNTERSUNK OVAL COUNTERSUNK 



BUTTON 




D 


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C 


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F 

3 


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Fig. 296. Various Forms of Cap Screw Heads 



(259) 



260 



MECHANICAL DRAWING 



ventions for multiple threads are distinguished from those for 
single threads by increasing the angle of the cross lines 




ffegu/ar low Head NecJ^ed Head /ess 



izo- 
Cup 



d' O/o at bottom 
of thread. 



nat/'iVof ffoundP/wt 



Fig. 297. Set Sceew Heads and Points 





Sitig/e LH. 



Doub/e R.H, 




Single Lfi, 



5lngfe RH ' Doudfe RH. 

Fig. 298. Conventional Representation op Multiple Threads 



and by a note indicating the kind of threads as double, triple, 
quadruple, etc. 



ADVANCED DRAWING 



261 



Methods of Indicating Finish. Wliere and how a part is to 
be finished may be shown by symbols or notes, or both. In case 
a hole is to be bored, drilled, reamed, cored, etc., a note is usually 
made in connection with the dimension figure. Fig. 299. A 
cylindrical surface to be turned, ground, polished, rough finished, 
etc., may have the method of finishing indicated in the same way. 
In case all surfaces of the object are to be finished and the method 
can be left to the workman 's judgment, a note may be made : 
FINISH ALL OVER. Where only certain surfaces are to be finished, 
I 




Fig. 299. Methods of Indicating Finish 

the character f may be placed across the lines which represent 
these surfaces viewed edgewise. Fig. 299. 

While the indication of finish is a very small part of a draw- 
ing, it is nevertheless a very important detail. The omission of a 
finish mark may mean the making of a large number of castings 
from a pattern on which no stock has been allowed for finish. 



Sketching from the Object 

PEEPARATORY INSTRUCTIONS FOR DRAWING PLATE 39 

Freehand sketches may be made by a designer to get an idea 
of the form of certain parts in working out his design, A 
designer or chief draftsman may use them as a means of con- 
veying his ideas to a junior draftsman. 



262 MECHANICAL DRAWING 

In case a machine is broken, time may often be saved by 
sketching the broken parts in the shop and having parts made 
to replace them instead of sending to the manufacturer of the 
machine for repairs. When a change of design is contemplated 
and the original drawings are not to be had, sketches of the 
parts affected may be made from the existing machine and the 
desired changes incorporated in the mechanical drawing made 
from sketches. When time permits and it is desirable to have 
a permanent record of the drawing a mechanical drawing should 
be made from the sketch, but in an emergency the sketch, if 
carefully drawn and checked, may be used as a shop drawing. 

In making the orthographic sketches of Chapter II, the fact 
that certain views of the object were shown in correct proportion 
and were dimensioned made the task of drawing the other views 
of the object to larger scale a simple process. 

The drawing of orthographic sketches from dimensioned per- 
spective sketches. Chapter III, increased the difficulty of selecting 
and arranging the views, and to some extent, the dimensions. 

Compared to sketching from orthographic and perspective 
views the average beginner will find the making of an ortho- 
graphic sketch from the object a rather intangible problem. He 
will fiLud it difficult to represent in outline an object which to the 
eye stands out in relief in light and shadow. At the same time 
he must keep in mind the fact that only two dimensions can be 
represented in each view. He is, also, confronted with the neces- 
sity of establishing center lines, datum lines, etc., which are not 
edges of the object but are of prime importance in the drawing. 

He must select dimensions to show the proper relation between 
the details of the object. These dimensions must also be selected 
to show similar distances on parts which are fitted to the object. 
He must use his judgment as to the accuracy with which each 
measurement should be made, as to the allowance for inaccuracies 
of workmanship, inaccuracies inherent in the process of manu- 
facture, etc. 

Selecting Views. In selecting the views of an object to be 
drawn, the principles developed in previous chapters should be 
used. In general only necessary views are drawn, but in the 
sketch additional views, partial views, sections, etc., may be 



ADVANCED DEAWING 263 

drawn in preference to complicating the necessary views with 
lines. 

Methods Used in Drawing. After an inspection of the object 
and after a decision has been reached as to what views are to be 
drawn, the student should place the object, if it is removable, so 
that he can obtain the required views without changing its posi- 
tion. Very often the shifting of the object leads to errors in. the 
relative position of the views, such as placing the left side view 
to the right instead of to the left of the front view. With the 
object always in the same position and the principles as to rela- 
tion of views, developed in former chapters, well in mind, such 
errors are not likely to occur. The views should show the object 
in as good proportion as can be obtained without scaling it. Time 
should not be wasted in taking dimensions at this stage and 
attempting to lay them out to scale. 

The first step in the construction of the drawing is to locate 
center or other reference lines. Circles should be constructed by 
first drawing two center lines at right angles. The radii should 
then be estimated from the intersection on these lines, and the 
circle drawn through the four points located. 

If the object is of cylindrical form, it will usually be found 
advantageous to draw the circular view first because of the ease 
with which the other views may be drawn by projecting the 
diameters from the circular view. In some cases where the views 
of the details of the object are interdependent, it will be necessary 
to construct two or more views simultaneously. 

The use of the coordinate paper greatly facilitates the align- 
ment and proportioning of the details in different views. The 
student should learn to use the ruled lines merely as a guide 
in locating and proportioning the views. The use of the squares 
as units of measurement for the purpose of drawing the object 
to scale is not to be considered ; for while it is admitted that their 
use will aid in proportioning the drawing, it is not one of the 
functions of a freehand sketch to show the object in accurate pro- 
portion, and the counting of the squares entails a serious waste of 
time. 

Selection and Arrangement of Dimensions. Wlien the views 
of the object are complete and have been checked carefully to 



264 MECHANICAL DRAWING 

make sure that they, together with necessary supplementary 
notes, fully represent the object, the question of dimensioning 
should next be considered. 

To dimension an object properly the draftsman must have 
some knowledge of the process through which it must go in the 
shop to become a finished product. If it be a casting he must 
know what dimensions the patternmakers will use in making the 
pattern; if it has finished surfaces he must know with what 
machines each is finished and give the dimensions in such a way 
that the machinist may use them directly. Example : The diam- 
eter of a part to be turned in the lathe should be given rather 
than the radius, since the most convenient and accurate method 
of measuring a cylindrical surface is by means of the caliper or 
micrometer. 

Enough dimensions should be given to determine completely 
the sizes and relation of the details of the object. When a sketch 
is made at some distance from the place at which it is to be used 
either to furnish information for a mechanical drawing or as a 
shop drawing, the draftsman must be sure that all necessary di- 
mensions are given. However, he should guard against giving un- 
necessary or useless dimensions in an attempt to avoid omitting 
necessary dimensions. All finished surfaces, special fits, etc., 
should be marked in such a way that they cannot be misunder- 
stood. The nature of the sketch admits of a freer use of explan- 
atory notes than would be tolerated on the mechanical drawing. 

Details which are required to be accurately located on the 
object should be referred by dimensions to center lines or finished 
surfaces. As the dimensions to be given are planned, the exten- 
sion and dimension lines should be drawn, but the dimension 
figures should not be inserted until all such lines are drawn. 

When the extension and dimension lines are drawn the arrow- 
heads should be made. 



MEASUREMENTS 



265 



MEASUREMENTS 



Measuring Instruments 



The following paragraphs contain a short description of the 
more common tools used in taking measurements from the object 
for the purpose of dimensioning a sketch. 

The Folding Rule. Rules are made of various lengths which 
may be folded and carried in the pocket. The smallest divisions 
are usually -^^ and -i^". Their construction makes the division 
into smaller fractions of an inch unwarrantable as these rules 
cannot be depended upon to read accurately to smaller units. 




Fig. 300. Folding Eule 



A two-foot rule will be found very serviceable where accuracy is 
not required. While convenient in measuring long distances, 
they are in general suitable only for rough work. Fig. 300. 

The Steel Tape. Steel tape may be had in lengths of 3 feet to 
200 feet or more. As in the case of the rules, their divisions are 
coarse and cannot be used for accurate measurements. Fig. 301. 

The Steel Scale. For accurate measurements steel scales are 
used. These scales may be had in lengths of V to 72'', and with 
various combinations of graduations on the two edges of each 
side. The most common graduations are I'', -^'^ ■^", ^V"> ^°d 
j^-,'\ Fig. 302. 

The Adjustable Square. Fig. 302 shows a square in which 
the blade is adjustable in the stock. The blade is an ordinary 



266 



MECHANICAL DRAWING 



steel scale with a groove made to receive a hook which serves to 
clamp the blade in the stock. The stock is furnished with, a level. 
This instrument will be found useful in many ways. 




Fig. 301. Steel Tape 




Fig. 302. Adjustable Square 



Calipers. Calipers are used for obtaining measurements of 
length or diameter where the scale cannot be applied directly. 
After they are set to the distance which is to be measured they 
are placed upon a scale and the distance read. Fig. 303 shows 
two forms of calipers, one adapted to outside measurements, such 
as diameters of shafts, etc., while the other is best suited to inside 
measurements, such as the diameter of holes. 

Other Devices, such as the plumb bob, straightedge, and sur- 
face gauge, may be of occasional use in taking measurements 
from the 6bject. 



MEASUREMENTS 



267 



Taking Measurements 

Having drawn the dimension lines, extension lines, and arrow- 
heads, there remain the taking of dimensions from the object and 
inserting them on the drawing. In doing this, judgment must be 
exercised in determining with what degree of accuracy each 
measurement should be taken. Examples : Dimensions between 
rough surfaces usually need not be given closer than the nearest 
iV" or aV", while the inside diameter of the bushing in which a 




Fig. 303. Inside Caliper. Outside Calipee 



shaft is to run would probably be given .003'' or ,004" larger 
than the diameter of the shaft. 

Judgment must also be exercised in determining whether 
irregularities such as the uneven thickness of eastings, lack of 
symmetry, apparent discrepancies in spacing of holes, etc., are 
intentional and essential to the design and construction of the 
object, or whether they are non-essentials which have come about 
through natural causes in the process of manufacture or poor 
workmanship, and should be eliminated from the drawing. 

The problems arising in the taking of measurements from the 
object are so varied that no attempt will be made here to discuss 
the subject fully. However, a few examples may be given which 
will illustrate the use of the measuring instruments and also the 
general principles involved in securing dimensions. 



268 



MECHANICAL DRAWING 



The distance between points on the same plane surface such 
as the distance between two parallel edges of the surface and the 




Fig. 804. Measuring a Linear Distance with the Scale 




Fig. 305. Measuring a Linear Distance with the Square 

length of cylinders may be measured directly with the rule or 
steel scale, as shown in Fig. 304. This method is only applicable 



MEASUREMENTS 



269 



for accurate measurement when the corners are sharp. When 
the corners are rounded, the same dimension may be obtained by 
using the square or caliper, as shown in .Fig. 305 or 306. 




Fig. 306. Measurixg a Linear Distance "with the Caliper 




Fig. 307. Eeading the Caliper Measurement from the Scale 



The use of the square here needs no explanation. The caliper 
must be set very carefully so that its points touch both surfaces 
between which the distance is to be measured, but not with 



270 



MECHANICAL DRAWING 



enough pressure to spring the caliper. The proper adjustment is 
obtained by means of the thumb screw on the adjustable caliper 
or by tapping the leg against a solid object in the case of the 
plain caliper. The distance between the points of the caliper is 




Fig. 308. Measuring the Diameter of a Cylinder with the Caliper 



measured with the steel scale, as shown in Fig. 307. Note that 
one point of the caliper rests against the end of the scale so that 
the operator's attention may be given entirely to reading the 
scale division at the other point. 




Fig. 309. Measuring the Diameter of a Hole with the Caliper 

The outside caliper is used in obtaining dimensions of curved 
surfaces. See Fig. 308. It is adjusted and the measurement 
taken from the scale as previously described. 

The inside caliper is used in measuring the diameters of holes 
and the openings between surfaces where the scale cannot be 
applied. Fig. 309. Measurements are obtained from the inside 



MEASUREMENTS 



271 



caliper by placing it over the scale, as shown in Fig. 310. Note 
that the scale is placed against a smooth surface and at right 




Fig. 310. Eeading Measurements ekom the Inside Caliper 




Fig. .Til. Measuring the Center to Center Distance of Equal Holes 



angles to it. One point of the inside caliper is placed against the 
smooth surface. By this method the scale division opposite the 
other point may be easily and accurately read. 



272 



MECHANICAL DRAWING 



When, as is very often the case, it is necessary to locate 
centers of holes with reference to each other or with reference to 
some finished surface or datum line, a difficulty arises from the 




Fig. 312. Type Problem. Cylinder Head. Freehand Sketch 



fact that a center line does not exist on the object and must be 
established or the dimension obtained in a roundabout way. 

In the case of two holes of equal diameter, the center-to-center 
distance may be obtained by measuring from the near edge of 
one to the far edge of the other. Fig. 311. The center-to-center 
distance of holes of unequal diameter may be obtained by meas- 
uring from the near edge of one to the near edge of the other and 
adding one-half the diameter of each. The distance from an edge 
or surface to the center of a hole may be had by adding one-half 
the diameter of the hole to the distance from the edge or surface 
to the near edge of the hole. 

Fig. 311 shows an object the form of which makes it necessary 
to use the caliper in measuring the distance between the centers 



MEASUREMENTS 



273 



of the two holes. The corners of cast parts are usually rounded 
or filleted. The radii of these curves are not easily measured, but 
usually it is unnecessary to measure them accurately. The radii 
of small fillets may often be estimated entirely by eye or the 
scale held against the object at one point of tangency and the 
radius estimated by placing the thumb nail at the division on the 




Fig. 313. Typical Objects for First Drawing from Model 

scale opposite the other tangent point. A very satisfactory 
method applicable in some cases is to place the object over a sheet 
of paper and trace around the corner or fillet with a sharp pencil. 
The center of the arc thus obtained may be found by trial with 
the dividers and the radius measured. 

Checking. Where a number of detail dimensions have been 
taken which make up the length of a larger detail or the whole 
length of the object, this over-all dimension should be checked 
by direct measurement as well as by addition of the detail 
dimensions. 



DATA FOE DRAWING PLATE 39 



Given : A simple machine part or model preferably finished 
all over. Fig. 313 shows typical objects for this plate. 
Required: To make a freehand orthographic sketch. 



274 MECHANICAL DRAWING 

Instructions: The following is a brief summary of the steps 
arranged in sequential order to be taken in making a sketch from 
the object. It is believed that by carefully observing the steps 
of this outline the draftsman will be able to make the sketch com- 
plete and accurate with a minimum amount of effort, and to do 
the work in the least amount of time. 

1. Select views. 

2. Draw views (proportioning details by eye without taking 
dimensions). 

3. Plan dimensions — draw dimension and extension lines. 

4. Draw arrowheads. 

5. Take dimensions from the object and place figures. 

6. Mark finished surfaces. 

7. Print all notes, including the name of the part drawn, the 
number required, and the material from which each part is to be 
made. 



For convenience in forming : 
.fine letters tiney ore divided intoz 
.stroi<es, Tliree tinings shioufd bei 
remembered about tine stroi<es : 
.for eacin letter, (I) tine number- : 



Fig. 314. Lettering Plate 39 



DATA FOR LETTERING PLATE 39 

Given: Plate 39 to reduced size. Fig. 314. 
Required: To make the plate to an enlarged scale. 



MEASUREMENTS 275 

DATA FOR DRAWING PLATE 40 

Given: The orthographic sketch. Plate 39. 

Required: To make a mechanical drawing from Plate 39. 



40 Jo^B, 



■'az^ 



\of strokes (2) the order in vvh/chz. 
\they ore made (3) the direction z 
\in which each strol<e is drawn z 
: Second only in importance to z 
'.the forms of the letters is their z 



Fir. 315. Lettering Plate 40 



4-1 ^^^rjAn/ Baz^^ 

zreiation to each other The finaiz 
ztest of good spacing is iegibiiity. z 
z All strokes should be made z 
zwith the hand and arm in the - 
zsame position. 123456 789 z 



Fig. 316. Lettering Plate 41 
DATA FOR LETTERING PLATE 40 
Given: Plate 40 to reduced size. Fig. 315. 
Required : To make the plate to an enlarged scale. 



276 MECHANICAL DRAWING 

DATA FOR DRAWING PLATE 41 

Given: The mechanical drawing, Plate 40. 
Eequired: To make a tracing from Plate 40. 




Fig. 317. Typical Model of Complete Machine 

DATA FOR LETTERING PLATE 41 

Given: Plate 41 to reduced size. Fig. 316. 
Eequired: To make the plate to an enlarged scale. 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 42 

The model for this plate should be a complete machine or 
some unit of a machine which is composed of several parts. The 



MEASUREMENTS 



277 



parts of the model then can be divided into several groups and 
each group assigned to a student.* Fig. 317 shows a typical 
model, the parts of which are divided into groups. Fig. 318. The 
detail drawings of this model will be used later (Plate 48) in 
making an assembly drawing. 




Fig. 318. Shoaving Groups of Parts of Machine for Assignment 



DATA FOR DRAWING PLATE 42 



Given : A part or group of parts of a machine. 

Bequired: To make an orthographic sketch of each part 
assigned by the instructor. 

Instructions : In making the sketches proceed according to 
the steps outlined for Plate 39. 

More than one part may be drawn on each sheet, provided the 
views are not too small or crowded too closely together. 

In drawing and dimensioning these objects the student should 
check each detail with the parts which are related to it or depend 
upon it in any way. 

Note should be made of the name of each part, the number 
required, and the material from which it is made. 

* This plan gives best results when there are from 3 to 6 students 
working on each model. 



278 MECHANICAL DRAWING 

DATA FOR LETTERING PLATE 42 

Given: Plate 42 to reduced size. Fig. 319. 
Bequired : To make the plate to an enlarged scale. 



z. Shifting of tine arm to obtain z 
zadvantageous positions for drawz. 
zing strokes in different direct- z 
zions is a Inabit whicln wHI never z 
z lead to rapid production of z 



Fig. 319. Lettering Plate 42 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 43 

When making the mechanical drawing, all of the parts in each , 
group should be drawn on one sheet if possible. The arrangement 
of the views should be such as to make the best use of the space 
available, and at the same time produce a pleasing effect for the 
sheet as a whole. This will require careful study. The solution . 
will depend largely on the draftsman's judgment. In general, it 
may be said that the distance between views of different objects 
should be greater than that between views of the same object. 
The enclosing rectangles for each view may be drawn lightly to 
make sure that sufficient space has been allowed for the drawing 
of all parts before drawing the views, or better yet, a rectangle 
equal in size to the enclosing rectangle for the views of each part 
may be cut from paper and moved about until the best possible 
arrangement is secured. 

Before starting to plan the arrangement of the sheet, the areas 
occupied by the bill of material and the title block should be laid 
out. The bill of material as shown in Fig. 279 contains the 



MEASUREMENTS 279 

reference figure corresponding to the one placed near the views 
of the object, the name of the object, the number required, and 
the materials from which it is made. The width of the bill of 
material is equal to the width of the title block, and the height 
depends upon the number of parts to be listed. See Fig. 279 for 
detail dimensions. 

In some shops the information referred to above is given for 
each part near the views of that part and is called a sub-title. 

The title for a sheet containing the drawings of several parts 
must be a general one in which the word * ' details ' ' usually takes 
the place of the name of the part drawn. See Fig. 322. It is 
often convenient to use different scales for the various objects, 
in which case the scale for each should be printed with the views 
of that part and the words, "Scales as noted," printed in the 
usual place in the title. 



z^— letters and at the same time ~ 

~/t will prevent the deveiooment z 

z.of the snap and swing which z 

z.gives the character to what is z 

^recognized as good lettering, z. 



Fig. 320. Lettering Plate 43 

DATA FOR DRAWING PLATE 43 
Given: The orthographic sketch, Plate 42. 
Required: To make a mechanical drawing from Plate 42. 

DATA FOR LETTERING PLATE 43 

Given: Plate 43 to reduced size. Fig. 320. 
Required : To make the plate to an enlarged scale. 



280 MECHANICAL DRAWING 

DATA FOR DRAWING PLATE 44 

Given: The pencil mechanical drawing. Plate 43. 

Required: To make a tracing of Plate 43. 

Instructions: The width of the top and left sides of the rec- 
tangle enclosing the bill of material and the vertical division lines 
should be object line width ( ^\ '').The horizontal lines between 
lines of lettering should be center line width (y^/')- 

DATA FOR LETTERING PLATE 44 

Given: Plate 44 to reduced size. Fig. 321. 
Required: To make the plate to an enlarged scale. 



z A drawing, the mechanical z 
zparf of winicli is well execuied, z 
zmay have its appearance spoiledz 
zby poor lettering. Lines shouldz 
zbe black and of uniform weight z 



Fig. 321. Lettering Plate 44 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 45 

One of the problems of the draftsman is to make detail draw- 
ings from the original layout of a machine in which the parts are 
shown assembled. On this assembly drawing some important 
dimensions may be given, others may be scaled from the drawing, 
and the remainder must be supplied by the draftsman himself. 
Since this course does not presuppose a knowledge of design, all 
necessary dimensions will be given on the assembly drawing from 
which the student draws this plate. 



MEASUREMENTS 



281 







, 


.1 


t 




F' 


uL 








.>^ 


^i^j- 


H' i! 


T ^ 






-^lobT 


II 

1 - 


— t^ 

1 1* 




-S I 


1 
1 




Ai 


rs 


5> 




L 
1 


!»■ 










^ 


1 












^9/ 
P, 




K 






* „/' 




' 





284 



MECHANICAL DRAWING 



The reading of the assembly drawing to get the correct form 
for each detail will in most cases require careful study. The dif- 
ferent parts may be distinguished when in section by various 
erosshatching for different metals and by the sectioning of adja- 
cent parts at opposite angles. But even with this aid the differ- 
ent views must be compared carefully to check the first impres- 
sion gained of the form of each part and to make sure that no 
detail has been overlooked. Each part of the object must be 
dimensioned completely. It is not sufficient to give a dimension 
on the views of one part and omit the same dimension on the views 
of another part, even though it is evident that the dimension is 
the same on both. 





De^a/7 of Cap 



Fig. 325. Leveling Screw 



DATA FOR DRAWING PLATE 45 

Given: An assembly drawing of a Leveling Screw, Fig. 
325 ; a flap valve. Fig. 326 ; and a letter press, Fig. 327. 

Required: To make freehand orthographic detail sketch 
of the object shown in Fig. 325, 326, 327, or any similar object 
as assigned by the instructor. 



MEASUREMENTS 



285 




Ph 



286 



MECHANICAL DRAWING 




Fig. 327. Letter Press 




J 




bJ 



ASSEMBLY 
BENCH DRILL PRESS 



Fig. 328. Type Pkoblem. Bench Drill Press 



(287) 



28S MECHANICAL DRAWING 

A Flap Valve is used to allow a liquid or gas, such as water 
or steam, to flow in one direction through a pipe but not in the 
other. Its parts, as designated by figures in circles in Fig. 326, 
are named as follows : 

1. Body. 2. Cap. 3. Valve. 4. Arm. 5. Cap Screw. 

A Leveling Scretv is used for leveling up work on a planer. 
Its parts, as designated by figures in circles in Fig. 325, are 
named as follows : 

1. Base. 2. Screw. 3. Cap. 

Fig. 327 shows a Letter Press. Its parts, as designated bj- 

figures in circles, are named as follows : 

1. Base. 6. Bolt. 

2. Plate. 7. Nut. 

3. Yoke Support. 8. Clamp. 

4. Press Screw. 9. Button Head Screw. 

5. Hand Wheel. 10. Yoke. 



43 jUn^£)^. 

z Careful attention to detail com\ 
~.bined with intelligent and per- : 
zsistent practice will do mucin to : 
zoffset lack of talent for lettering^ 
z 2357 9861 45309 728695 : 



Fig. 329. Lettering Plate 45. 

DATA FOR LETTERING PLATE 45 

Given: Plate 45 to reduced size. Fig. 329 
Required : To make the plate to an enlarged scale. 



MEASUREMENTS 



289 



DATA FOR DRAWING PLATE 46 

Given: The orthographic sketch. Plate 45. 

Required: To make a pencil mechanical drawing from 

Plate 45. 

DATA FOR DRAWING PLATE 47 

Given: The pencil mechanical drawing. Plate 46. 
Required: To make a tracing of Plate 46. 




3ZZ^ 



Fig. 330A. Details of Bench Grixder 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 48 

An AssemUy or General Drawing is made for showing the 
position and relation of parts of a machine or structure. Usually- 
only the most important dimensions are given. Example: 
Fig. 328. 



290 



MECHANICAL DRAWING 



DATA FOR DRAWING PLATE 48 



Given : The detail drawings of a bench grinder, Figs. 330A 
and 330B ; screw punch, Fig. 331. 







O ) Washer 
'■ I 'Wanted 



9^ 



5q. HeadSefScreiy 

/ iYanfeif Mead/ess RH. CapScretrs 
'_„^_^ 5ef3crvyy 4 IVanted atVantsif 



"ya 






^r^r/// i_iij ic ^^ ^^ *JiF yr 



roofFesf 



,J_ 



T . P" 



[] 



- - a ^ K - / ■; 



La 

/O TMs.per inc. 



^ 



Fjr/ish af/c^ref 
0(/fs/def/af?^e /ns/'a/e r/ange 

2 „ of £ac/7 Bi/ffi^n HeadBo/f 
/ Wanted 




Tool ffes f HoMer 



Bracket 



^1_^ 



N$ -^ 

T — t '0^ 



K® 



•l^l i, 



ru 



>r 






L-^- 






u 



^1 






Fr=4rzrd 



^rrt^q 



U^^ 



Tfe 




Fig. 330B. Details op Bench Grinder 



MEASUREMENTS 



291 




I'bn// Beaded eJ^e No 30 Dr/// 
S Use speciaJ too/ Use spec/a/ c/r/7/ 



E5 ^ 



Section shoyy/ng ba// /le/ct 
in p/ace by beaded edqe 
of socket 




^-^ 



Locate grooi^e offer assembJing 
A — \ ■ — f >Tr 




Fig. 331. Details of Screw Punch 



292 MECHANICAL DRAWING 

Required: To make a pencil mechanical drawing from the 
details of the objects shown in Figs. 830A and 330B or 331, or any 
similar problem assigned by the instructor. It is suggested that 
an assembly drawing may be made from the student detail draw- 
ings of Plate 43. 

DATA FOR DRAWING PLATE 49 

Given: The pencil mechanical drawing. Plate 48. 
Required: To make a tracing of Plate 48. 

Architectural Drawing 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 50 

The average man who contemplates building a house for him- 
self finds it a great convenience to be able to make scale drawings 
of sufficient accuracy to test his ideas of the arrangement of 
rooms, dimensions, proportions, general appearance, etc., and as 
a means of conveying his ideas to an architect or contractor. 
The drawings should consist of floor plans and views of each side 
of the house, known as elevations. 

The general arrangement of rooms on the first floor will 
depend on such things as the nature of the site, the owner 's ideas 
of household conveniences, etc. As a general principle, the rooms 
which are used the largest percentage of time are given the most 
favorable location for light and ventilation. As an example, the 
living room is quite frequently arranged to have a south and east 
exposure. 

In all rooms, the location of furniture, doors, windows, etc., 
should be carefully considered as the plan for the house is pro- 
gressing. The kitchen in the average small house is planned to 
save steps for the housewife. The sink, stove, table, and cup- 
boards should be arranged with a vifew to convenience. 

In the average house, economy of space is a feature worth 
striving for, as the cost of the house will range from 15 cents to 
22 cents per cubic foot. 

The plan of the second floor will depend somewhat on that of 
the first floor. The partitions on the second floor should be 



MEASUREMENTS 



293 




Fig. 331A. Extra Plate 




Fig. 331B. Extra Plate 



294 



MECHANICAL DRAWING 




F/n/3h 
/ran - Drop B/ack 
Copper-Oj(/if/zeafB/acA 



Fig. 331C. Extra Plate 



MEASUREMENTS 



295 



directly over those on the first floor, as far as this arrangement 
can be made. The position of the stairs must be considered and 
space enough allowed for steps to reach the second floor. As a 







LIV1N<^ ^a.oo^^ To Bt^ 
OF «e 1. dit.l>R.<HIA 

Pine- , '^Ji«&'. 



Fig. 332. First Floor Plan of House 



guide in laying out stairs, the sum of the tread and rise should 
be about 17" to 17^", with a tread not less than 9" wide for front 
stairs or 8" wide for back stairs. 



296 



MECHANICAL DRAWING 



In locating the bathroom, care must be taken to make it 
possible for the pipes and drains to lead down through the walls 
of the first floor. In a cold climate there is danger of freezing 



JiN Eoof 




Fig. 333. Second Floor Plan of House 

if they are put through an outside wall. Wherever possible, 
plumbing should be minimized. It is well, therefore^ to have 

bathroom, kitchen, and basement water and sewer connections in 
the same vertical wall. 



MEASUREMENTS 



297 




298 



MECHANICAL DRAWING 




t: 

o 

f-. 

< 
> ■:. 

J 

, < 

Q '0 



MEASUREMENTS 



299 



A bathroom should not be less than 5' 6" one way with not 
less than 49 sq. ft. of floor space. In planning bedrooms, there 
should be windows on two adjacent sides, if possible, to provide 
light and good ventilation. Bedrooms may be as small as 9' 6" 







32ZZ6 




TvPicAL^ De-jaius of 3oor.£> <%Winoovjs 
Fig. 336. Details of Door and Window 



by 11' 6", if well planned. The spaces for beds, dressers,, etc., 
should be considered with reference both to natural and artificial 
light and to necessary wall space. All upstairs rooms should be 
provided with ample closet room. Other considerations entering 
into the problem of planning the upstairs is the type of roof, 
position of chimneys, etc. Electric wiring, especially for outlets, 



300 MECHANICAli DRAWING 

and pipes for either hot air or for steam or hot water should be 
thought out as the plans for the two floors are made. 

"When the floor plans have been arranged, the elevation and 
possibly a perspective of the house should be drawn. If the 
appearance is not satisfactory, the plans for the floors may need 
altering. It is not uncommon for plans to be worked over a 
number of times to meet the needs of both owner and builder. 

DATA FOR DRAWING PLATE 50 

Given: The two floor plans, the side and front elevations 
of a house, with details, as shown in Figs. 332, 333, 334, 335, 
and 336. 

Required: To rearrange the floor plans, if desired, and to 
design the other side elevation and the rear elevation, or any 
similar problems assigned by the instructor. 

Note. The stuvdent may change the elevations shown in Figs. 
834 and 335 if his second floor plan demands a different arrange- 
ment of windows or changes in the roof. 

Instructions: It will be found very convenient to draw the 
flrst floor plan and then lay out the plan of the second floor on 
transparent paper stretched over the first floor drawing. 

Many measurements are thus copied by tracing ; an accurate 
register of all first floor data in comparison with that for the 
second floor is thus made, and mistakes are less apt to occur. In 
a similar manner the elevations may be drawn over the plans but 
of course in this case all the vertical measurements must be made 
with a scale. The particular advantage in this method of draw- 
ing elevation views is to secure correct horizontal dimensions, 
window and door positions, etc. 

PEEPAEATORY INSTRUCTIONS FOR DRAWING PLATE 51 

After the construction of a house has progressed until the 
walls are covered with plaster on the inside and with siding on 
the outside, and after the roof is in place, the framing construc- 
tion is not apparent. But in order to build a house which will 
stand firm in wind and will not let in the rain, the carpenter 



ARCHITECTUEAL DRAWING 



301 




302 



MECHANICAL DRAWING 



must consider carefully problems of framing construction. Figs. 
338, 339, 340, and 341 give in detail typical construction for a 
small house. 




Pig. 338. Perspective of Park House 




Fig. 339. Perspective of Framing Construction of Park House 



MEASUREMENTS 



303 



DATA FOR DRAWING PLATE 51 

Given: The perspective sketches, Figs, 338 and 339; the 
plan, Fig. 340 ; and the cornice detail, Fig. 341, for a small park 
house. 

Required: To draw the orthographic views showing the 
framing and details of construction for the park house or any- 
similar object as assigned by the instructor. 

^ 



^11 ly y ■ 



■I K y 



^J6*- 



W.-1 



TO 



/ 






H i i\ ^ 



II ' '11 



is'-o"- 



XVTF 






Center p/er / 



r~i 



L_z: 



r n P/afe cross-corner 
r~T I braces 






Tvrr 



!^ 1. ::_ Z-jj 



U.--J\. 



<-/5->-j 



Fig. 340. Plan of Pake House 



304 



MECHANICAL DRAWING 




/f . P/afe 2x4 „ 

3. 6/rt E-e'JK4.Morfised//ffo posts 

C Frieze ^^ „ 

D furr/m strips ^"-x/^ 

£. MoM//7q 5"* 

/■ //aiiini^ biScAs 

6 ni//nai betiveen rafters 

O ' Furnn^ strips ^"^ 'I" 






/^ sq. strips scretvect to cap. 
posts. anc!t soffit tor 
fastenings 



Detaif of Sheath fng 







■ I 

t 

Petail of Si/I and Footings 



^\^'~-\Bioct( naiied to joists 
_ i| I j "fie rod yy/th nut a, 



and (vasher 

Fig. 341. Cornice Details 




CHAPTER VI 

- ISOMETRIC AND CABINET DRAWING 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 52 

Isometric Drawing is a mechanical method of representing 
objects pictorially. The object may appear somewhat distorted 
when drawn by this method, but to one who Is not accustomed 
to reading orthographic drawings or for one who is unable to 
make a good freehand perspective drawing, it serves the purpose 
of making clear the general form of the object. By placing 




.^ 


<r 


^ 


\ 


■^ 


\. ^ 


^. 


+ 


^^^ 


\ 












Fig. 342. The Cube in Isometric 



dimensions on it the isometric drawing may be used as a working 
drawing. 

Fig. 342 shows the isometric of a cube. The cube appears as 
shown in this figure when it is viewed (as in orthographic draw- 
ing) with a diagonal of the cube coincident to, or parallel with, 
the line of sight. When in this position the three edges meeting 
in the near corner are represented by lines 120° apart. 

The three lines 120° apart are the axes parallel to which all 
measurements are made in isometric drawing. 

Non-Isometric Lines. A line which is not parallel to one of 
the three axes is a non-isometric line. A non-isometric line is 
drawn by referring points on the line to the axes by means of 

305 



306 



MECHANICAL DRAWING 



coordinates. Fig. 343 shows a rectangular solid on the top face 
of which is a non-isometric line having a curved and a straight 
portion. The position of the point D is determined in the 
isometric by transferring lengths AB and AC from the ortho- 
graphic views with the dividers and drawing lines B D and C D 
parallel to the axes. In some cases where a figure containing non- 
isometric lines is to be drawn, it is convenient to enclose the figure 
in a rectangle. The hexagon in the side face of the rectangular 
solid, Fig. 343, and the circle enclosed in a square, Fig. 343, are 
illustrations of such cases. 













n 






^ 


1 








s 


1 r,l 














B 




y 


/ 


y 




A 










c 








Fig. 343. Locating Points on Non-Isometkic Lines Using Two 
Coordinates 



When non-isometric lines do not lie in a face of a rectangular 
solid, three coordinates are necessary to locate' points on each 
line. In drawing the isometric of the frustum of the hexagonal 
pyramid. Fig. 344, the base is first enclosed in a rectangle and the 
points on the top face are located by three coordinates as shown. 
The lengths A B, B D, and D E are taken from the orthographic 
views and laid off on the isometric in the directions parallel to 
each of the three axes, respectively. 

Isometric Circles. Circles may be drawn by locating points 
as described above, or by the four-center method shown in Fig. 
345. Point A, the center of the smaller arc, is located by laying 
off AB = BC. The center D for the larger arc is located by 
drawing A D through A perpendicular to B E. The other centers 




Fig. 344. Locatiiv^g Points on Non-Isometric Lines Using Three 

Coordinates 




Fig. 345. A Four-Center Method for Drawing Circles in Isometric 

(307) 




Fig. 346. Methods of Drawing Circles and Arcs 



n— 
\-f7 



— I — I 



Lj 



-I I 




K^^ 



Fig. 347. Type Problem. Study Table. Orthographic Views 

(308) 






Fig. 348. Type Problem. Isometric Drawing of Study Table 




Fig. 349. Type Problem. Cabinet Drawing op Study Table 

(309) 



310 



MECHANICAL DEAWING 



are located in a similar manner. The ares are tangent at the 
point F. The four-center method is an approximation and is 
usually suitable only for full circles. When an arc is drawn 
which must pass through certain points the plotting method is 
preferable. Fig. 346. 



r">- 



-«rV 



^i. 



M 



\, Defai/of 

" Corner Construction 



U-i — js" *- 



r±T c 






Fig. 350. Taboret 



DATA FOR DRAWING PLATE 52 



Given: The orthographic views of a taboret. Fig. 350. 

Required: To make an isometric (or cabinet drawing) of 
the object shown in Fig. 350 or any similar object assigned by 
the instructor. For cabinet drawing instructions see page 314. 

Instructions: 

1. Make an orthographic drawing to scale. 

2. Draw lines for the isometric drawing in the directions of 
the three axes : One vertical, and one each to the right and to the 
left, making 30° with the horizontal. 



ISOMETRIC AND CABINET DRAWING 



311 



3. Decide which of the general dimensions of the object is 
to be measured in the direction of each axis. 

4. Locate a certain point, usually an extreme corner of the 
object, at the intersection of the lines drawn as directed in 2. 




Fig. 351. Type Problem. 



Planing Jig for Eod Brass. 
Views 



Orthographic 



5. Transfer actual lengths from the orthographic drawing 
with the dividers, taking care to lay them off in the direction of 
the proper axis. 

6. Draw the necessary lines through the points located, re- 
membering that lines of the object which are parallel to a general 
dimension of the object should be drawn parallel to the axis 
representing that dimension. 

7. All other lines must be determined by locating points as 
described on page 306. 




Fig. 352, Type Problem. Isometric of Jig for Rod Brass 




(312) pjq^ 252^ Type Problem. Cabinet of Jig for Eod Brass 



ISOMETRIC AND CABINET DRAWING 



313 



DATA rOR DRAWING PLATE 53 

Giren: The orthographic views of a crosshead brass. Fig. 
354. 

Required: To make an isometric (or cabinet drawing) of 
the object shown in Fig. 354, or any similar problem assigned 
by the instructor. For cabinet drawing instructions see page 314. 




Fig. 354. Crosshead Brass 
Instructions : 

1. Proceed in drawing the straight lines as for the preceding 
plate. 

2. To draw the circles by the four center method, first deter- 
mine the center by the method of coordinates. 

3. Draw a figure representing a square which just circum- 
scribes the circle. Care must be taken to draw this figure so 
that it will appear to lie in the same face of the object as the 
circle to be drawn. The direction of the sides of this figure will 
correspond to those representing one of the faces of the cube. 
Fig. 345. 

4. Draw the curves by the method given under, ''Isometric 
Circles." 



314 



MECHANICAL DRAWING 



Cabinet Drawing 

PREPARATORY INSTRUCTIONS FOR DRAWING PLATE 54 

Cabinet Drawing is similar to isometric in that measurements 
are made parallel to three axes. One of the axes is horizontal, 
the second vertical, and the, third 45° to the horizontal. Fig. 355. 
Actual lengths are measured parallel to the horizontal and ver- 
tical axes and one-half the actual lengths are measured parallel 




Fig. 355. Cabinet Drawing of Cube 




Fig. 356. Example of an Object with Circles and Arcs Parallel to 

One Plane 

to the 45° axis. It should be evident that objects which involve 
the drawing of irregular shaped figures which are located in or 
parallel to the front surface of the object can be represented 
more easily by cabinet than by isometric, inasmuch as such 
figures will be drawn in their true form in a cabinet drawing. 
For example, an object which has a number of circles parallel 
to one plane is more easily represented in cabinet than in 
isometric, since the circles can be drawn with the compass. 
Fig. 356. 



ISOMETRIC AND CABINET DRAWING 
DATA FOR DRAWING PLATE 54 



315 



Given: The orthographic views ol a taboret. Fig. 350, 
Required: To make a cabinet drawing of the object shown 
in Fig. 350, or any similar object assigned by the instructor. 




Fig. 357. Air Starter Bearing 



Instructions ; 



1. Make an orthographic drawing to scale. 

2. Draw lines for the cabinet drawing in the direction of the 
three axes; one vertical, one horizontal, and one at 45°. 

3. Decide upon the general dimension of the object to be 
measured in the direction of each axis. 

4. Locate a certain point, usually an extreme corner of the 
object, at the intersection of the lines drawn as directed in 2. 

5. Transfer actual lengths from the orthographic drawing 
with the dividers for the measurements parallel to the horizontal 
and vertical axes, and one-half actual lengths for the measure- 
ments parallel to the 45° axis. 



316 



MECHANICAL DRAWING 



6. Draw the necessary lines through the points located, re- 
membering that the lines of the object, which are parallel to a 
general dimension of the object, should be drawn parallel to the 
axis representing that dimension. 

7. Lines not parallel to the axes must be located by the same 
method of plotting points used for the isometric drawing and 
described on page 306. 




Pjg. 358. Type Problem. Sparker Body 



DATA FOR DRAWING PLATE 55 

Given: The orthographic views of a crosshead brass. Fig. 
354. 

Required: To make a cabinet drawing of the object as 
shown in Fig. 354, or any similar problem assigned by the 
instructor. 

Instructions: 

1. Proceed in drawing the straight lines as for the preceding 
plate. 



ISOMETRIC AND CABINET DRAWING 



317 



2. The circles which are in or parallel to the front face of 
the object may be drawn with the compass. All others must be 
determined by plotting points. The object should be placed, if 
possible, so that the circles can be drawn with the compass. 

DATA FOR DRAWING PLATE 56 

Given: The orthographic views of a sparker body. Fig. 
358. 

Required: To make a cabinet drawing of the object shown 
in Fig. 358, or any similar object assigned by the instructor. 




Fig. 359. Bosch Magneto Cam 



Instructions: 

1. Make an orthographic drawing to scale. Draw lines for 
the cabinet drawing in the direction of the three axes; one ver- 
tical, one horizontal, and one to the right or the left, making 45° 
with the horizontal. 



318 MECHANICAL DRAWING 

2. Transfer measurements by the same general method used 
in isometric, laying off only one-half the actual lengths in the 
direction of the 45° axis. 

3. Circles or curves in the front face of the object or planes 
parallel to the front face should be drawn in their exact size and 
form. All other circles and curves must be plotted. 



CHAPTER VII 

GEOMETRICAL CONSTRUCTIONS 

PROBLEM 1 

Given: A straight line or arc AB. 
Required: To bisect AB. Fig. 360. 




Fig. 360. To Bisect a Line or Arc 



Instructions : With A and B as centers describe ares inter- 
secting at C and D. The line CD bisects the straight line AB 
at F and the arc at E. 




a b c d 

Fig. 361. To Divide a Lixe Into a Number of Equal Parts 



PROBLEM 2 

Given: A straight line AB. 

Required: To divide AB into any number of equal parts, 
as five. Fig. 361. 

319 



320 



MECHANICAL DRAWING 



Instructions: Draw line AC at any angle with AB and lay 
off on it five equal spaces, using any convenient unit. Draw 
5 B and parallels to it through 1, 2, 3, 4. a, b, c, d are the required 
divisions. 

Note. A line such as AB in Problems 1 and 2 may be 
divided by means of the dividers, as described on page 129. 

PROBLEM 3 

Given : An angle ABC. 
Required: To bisect angle ABC. Fig. 362. 

c 




Fig. 362. To Bisect an Angle ' 

Instructions: With B as a center, draw an arc AC of any 
radius. With A and C as centers describe arcs of equal radius 
intersecting in D. B D bisects the angle ABC. . 




Fig. 363. To Trisect a Eight Angle 



PROBLEM 4 

Given: A ngr/i;^ angle A B C. 

Required: To trisect angle ABC. Fig. 363. 



GEOMETRICAL CONSTRUCTIONS 



321 



Instructions: First Method. With B as a center, draw an 
arc A C of any radius. With A and C as centers and the same 
radius, draw arcs B D and B E. The angles thus formed are 30°, 




Fig. 364. To Trisect a Eight Angle with the Triangle 

Second Method. An angle may be divided into any number 
of equal parts by drawing an arc such as A C in Problems 3 
and 4 and stepping off equal distances on the arc, with the 
dividers. 




Fig. 365. To Construct a Square 



PROBLEM 5 

Given: The length of the side of a square, AB. 
Required: To construct the square. Fig. 365. 



322 



MECHANICAL DRAWING 



Instructions: First Method. Draw arc B D C with A B as a 
radius. Bisect arc BDC (Problem 1). AD is now at right 
angles to AB. With centers at D and B draw arcs of radius 
AB intersecting in the fourth corner of the square. 




Fig. 366. To Construct a Square with the Triangle 



Second Method. The square may be constructed with the 
triangles and T-square. Fig. 366. BE and AD are drawn at 
right angles to AB and A E at 45° to A B. DE is drawn 
through E parallel to AB. ' 





Ml 

A 




N 

\ 




L 









6 


X 


H 




V 


/ 


w 


s 


/ 


f 


\ 


/ ^ 


y\ 




A 




B 






P> 


<. > 


CQ 





Fig. 367. To Construct an Octagon 

PROBLEM 6 
Given: The length of the side of a regular octagon. 
Required : To construct the octagon. Fig. 367. 



GEOMETRICAL CONSTRUCTIONS 



323 



histructions : First Method. Draw arc B C and A D and 
bisect each as with the lines P M and Q N. Bisect the exterior 
right angles and draw A C and B D equal to A B. Connect 
C and D. Make FG and EH equal to FE and draw LO 
through GH. Make L G, GM, HN, and HO equal to CF or 
E D. Connect C, L, M, N, 0, and D. 



/ 




IN 

K 


/ 


/] 


G 


A 


H 


X 


'\ 


/ 


^y 


D y 




V 


B / 




/ 









Fig. 368. To Construct an Octagon avith the Triangle 



Second MetJiod. The octagon may be constructed with the 
T-square and 45° triangle, Fig. 368. BD is drawn at 45° to 
A B and equal in length to A B. AM and B N are drawn per- 
pendicular to A B. C D is drawn parallel to A B. F H is at 45° 
to AB and LO parallel to AB. The figure may now be com- 
pleted by drawing the following lines in the order given. AC, 
CL, DO, LM, ON, MN. 




A^^ -^B 

Fig. 369. To Construct a Hexagon 



PROBLEM 7 
Given: The length of the side of a regular hexagon. 
Eequired: To construct the hexagon. Fig. 369. 



324 



MECHANICAL DRAWING 



Instructions : First Method. With a radius A B and centers 
at A and B, describe arcs meeting at C. With C as center and 
the same radius, draw a circle. With the same radius set off the 
arcs B D, D E, E F, F G, and G A. The side of the hexagon 
equals the radius of the circumscribed circle. 




Pig. 370. To Construct a Hexagon with the Triangle 

Second Method. Draw a circle with a radius equal to the 
side of the hexagon. Draw a horizontal or vertical diameter A B, 
Fig. 370, depending on the position of the hexagon. Draw lines 
with the 60° - 30° triangle through A and B, striking the circle. 
Complete the figure by horizontal or vertical lines, as the case 
may require. 




Fig. 371. 



To Construct a Tangent to a Circle Through a Point Outside 
THE Circle 



FBOBLEM 8 
Given: A circle and a point outside the circle. 
Required: To draw a tangent to the circle through the 
point. 



GEOMETRICAL CONSTRUCTIONS 



325 



Instructions: First MetJiod. With a radius A B and center 
at A, describe arc B C. With a radius equal to the diameter of 
the circle cut the arc at C. The chord B C strikes the circle in D, 
the point of tangency. B D is perpendicular to the tangent A D. 
Fig. 371. 




Fig. 372. 



To Construct a Tangent to a Circle Throlgh a Point with 
THE Triangle 



Second Method. The tangent may be drawn with a straight 
edge, as shown in Fig, 372. The point of tangency may be 
found as shown in Fig. 195, page 184. 



PROBLEM 9 

Given: Two arcs. 

Required: To draw a line tangent to both arcs. 

Instructions: First Method. Make EF equal to AG, Fig. 
373, and draw a tangent through A to the small circle CF, as 
in Problem 8. Extend B H and draw A G at right angles to A C. 
Join GK. 





Fig. 373. 



To Draw a Line Tangent 
to Two Arcs 



FiG.»374. To Draw a Line Tan- 
gent TO Two Arcs with the Tri- 
angle 



Second Method. The tangent may be drawn with a straight- 
edge, as shown in Fig. 374. The points of tangency may be 
found, as shown in Fig. 195, page 184. 



326 



MECHANICAL DRAWING 



PROBLEM 10 

Given: Two straight lines intersecting at any angle. 

Required: To draw an arc of given radius tangent to the 
two lines. Fig. 375. 

Instructions : First Method. With radius equal to the given 
radius, draw ares from two different points in each line. Draw 
tangents to each pair of arcs. The intersection of these lines, H, 
is the center of the tangent arc. Perpendiculars from this point 
to the tangent lines locate the points of tangency K, L. 





Fig. 375. To Dra-\v an Aec Tan- 
gent TO Two Intersecting Liives 



Fig. 376. To Draw an Arc Tan- 
gent TO Two Intersecting Lines 
WITH THE Triangle 



Second Method. Fig. 376. Draw a line at right angles to 
each of the intersecting lines with the triangles, as described on 
page 125. Lay off B D and E C equal to the radius of arc. Draw 
lines D F and E F parallel to A B and A C, respectively, as 
described on page 125. F is the center of the arc. The points 
of tangency K and L may be located as described on page 184. 



GEOMETRICAL CONSTRUCTIONS 



327 



PROBLEM 11 

Given: Two circles of different diameters. 
Required: To draw a circle of given radius tangent to 
both circles. Fig. 377. 




Pig. 377. To Draw a Circle of Given Eadius Taxgext to Two Circles 

Instructions: From the center of circle A with a radius 
equal to R plus the radius of A, and from the center of B with 
a radius equal to R plus the radius of B, draw two arcs inter- 
secting at C, which is the center of the required circle. The 
points of tangency are found by joining the centers of the circles. 

PROBLEM 12 

Given: Two parallel straight lines A B and C D, 
Required : To draw arcs of circles tangent to A B and C D 
and passing through E. Fig. 378. 




A B 

Fig. .378. To Draw Arcs Tangent to Two Straight Lines Through a 

Point 

Instructions: Bisect BE and CE and erect perpendiculars 
to AB and CD at B and C. F and G are the required centers. 
The arcs are tangent at E. This is called a reverse or an 0. G. 
curve. 



328 



MECHANICAL DRAWING 



PROBLEM 13 



Given: The length of the major and minor axes of the 
ellipse, OA and OB. 

Required: To construct the ellipse. 




Fig. 379. Trammel Method of Drawing ax Ellipse 

Instructions: Trammel Method. Fig. 379. Mark off on a 
card, C D equal to B and C E equal to O A. Keep the trammel 
with the point D always on the major axis and point E always 
on the minor axis. Move the trammel and mark points opposite 
C to form the curve. 



-^ 




Fig. 389. Construction Method of Drawing ax Ellipse 



Second Method. Fig. 380. Draw circles of radii equal to the 
major and minor axes. Draw any radii C, D, etc. ; draw 
C G, D H, etc., perpendicular to A, and E G, etc., parallel 
to A. G, H, etc., are points on the curve. 



INDEX 



Accurac}', 133 

Accuracy of measurements, 267 

Acme threads, 253 

Adjacent parts, crosshatching, of, 229 

Adjustable square, 266 

Angle of inclination, 13 

Angles 

dimensioning, 89 
Architect's scale, 127 
Architectural drawing, 292 
Arrangement of dimensions in ortho- 
graphic sketch, 76 
Arrangement of views on sheet, 140 
Arrowheads, 38 
Assembly drawing 

purpose of, 289 

details from, 2S0 
Axes, derivation of. Isometric, 305 

Balancing a title. 27. 140 
Bill of material, 247 
Bill of stock, 226 
Blueprinting, 166 
Board, drawing, 15, 118 
Bolt, tap, 258 
Bolts and nuts, 255 
Border line, 172 
Border rectangle, 20, 133 
Bow dividers, 132 
Bow pen, 132, 171 
Bow pencil, 132 
Breaks, conventional, 229 

Cabinet drawing, 314 
Calipers, 267 
Cap screw, 25S 
Center lines 

circular, .100 

principal, 100 

radial, lOO 

secondary, 100 
Circle 

drawing with bow compass, 171 

sketching,. 101 
Circles 

concentric, in perspective, 47 

dimensions of, 100 

Isometric, 306 
Circular edges, 93 
Cloth, tracing. ICl, 165 
Compass, 170 



Concentric circles in perspective, 47 
Constructive stage 

in perspective, 18 

of orthographic sketch, 74 

of mechanical drawing, 135 
Conventional cross-sectioning, 230 
Coordinate paper, 263 
Corners, representation of, 69 
Crosshatching 

adjacent parts, 99, 229 

conventional, 230 
Crosshatch lines, 172 
Cube 

in perspective, 13 

measure, definition of, 34 

measure in new positions, 57 
Cylinder 

measure, horizontal, 52 

measure, in new positions, 58 

measure, vertical, 44 
Cylindrical surfaces 

dimensions of, 100 

representation of, 92 

Development of a surface 

prism, 190 

cylinder. 197 

cone, 203 

pyramid. 212 
Diameter 

measuring inside, 270 

measuring outside, 270 
Dimension 

figure 137 

form, 37, 77 

lino, 13C> 
Dimensions 

arrangement of in orthographic 
sketch, 76 

selection and arrangement, 263 
Dimensioning 

angles, S9 

general principles of, 136 

cylindrical surfaces and circles, 100 

radius, 150 
Distance 

measuring center to center of holes, 
271 

measuring linear, 268 
Dividers, 130 
Dotted lines, 171 



329 



330 



INDEX 



Drawiug 

an ellipse, 47 

board, 15, IIS 

cabinet, 314 

from the object, 261 

Isometric, 305 

paper, 15, 119 
Drawing instruments 

bow dividers, 132 

bow pen, 132 

bow pencil, 132 

compass, 128 

dividers, 130 

ruling pen, 167 

Edges 

circulai', representation of, 93 

inclined, 82 

invisible, 69 

straight, 69 
Ellipse, to draw and test, 47 
Enclosing rectangle, 133 
Enclosing solid in perspective, 34 
Engineer's scale, 127 
Eraser, 132 
Erasing shield, 132 
Extension lines, 136 

Fastening paper to board, 15 
Figures 

and notes, 137 

dimension, 137 
Filling lettering pen, 103 
Finish, methods of indicating, 261 
Finishing stage 

for mechanical di'awing, 135 

for orthographic sketch, 76 

in perspective, 18 • 
Folding rule, 265 
Foot marks, 30 

Foreshortening, definition of, 13 
Fraction and whole number, 137 
Furniture and cabinet problems, 231 



General drawing, 289 
Geometrical constructions. 



319 



Heads, arrow, 38 
Heights of letters, 137 
Horizon, definition, 10 
Horizontal lines, ruling, 126 

Inch marks, 30 
Inclination, angle of, 13 
Inclined edges, 82 
Inclined surfaces, 81 
Ink, black, 167 



Inking 

order of, 172 
Inside diameter, measuring of, 270 
Instruments 

drawing, 128 

measuring, 265 
Invisible edges, 69 
Isometric drawings, 305 

derivation of axes, 305 

Isometric circles, 306 

Isometric lines, 305 

locating points with three coordi- 
nates, 307 

locating points with two coordinates, 
306 

non-Isometric lines, 305 

Joints, 232, 233 

Lead, 258 
Lettering 

foi'm and proportion of, 22 

inclined, lower case, slope of, 192 

in ink. 25, 102 

in pencil, 24 

pencil, 28 

plate, 28 

position of hand in, 24 

preparation of tracing cloth. 102 

slope, 194 

spacing of, 23 

strokes for, 28 
Levels 

scale of, cylindrical objects, 45 

scale of, rectangular objects, 31 
Line 

border, 172 

dotted, 76 

invisible, 76 

notation, 171 

object, 172 

table, 35 
Linear distance, measuring, 268 
Line, center 

circular, 100 
' principal, 100 

radical, 100 

secondary, 100 
Lines 

Crosshatch, 172 

extension and dimension, 136 

in perspective, direction of, 11 

Isometric, 305 

non-Isometric, 305 

object, 171 

Parallel lines, 125 
Perpendicular lines, 125 



INDEX) 



331 



Machine drawing, 247 
Machine screws, 258 
Marks, foot and inch, 30 
Material, bill of, 247 
Measure 

cube, definition, .34 

cube in new positions, 57 

cylinder, horizontal, 52 

cylinder in new positions, 58 

cylinder, vertical, 44 
Measurements 

accuracy of, 267 

center-to-center of holes, 272 

in foreshortening, 13 

in perspective, 31 

linear distances, 268 

radii, 273 

taking of, 267 
Measuring Instruments. 265 
Multiple thread, 258 

Notation of lines, 171 
Notes, 137 

Number and fraction. 43 
Nuts and bolts, 255 

Object 

lines. 172 

sketching from. 261 
Orthographic 

front and side, 81 

review, orthographic sketching, 104 

sketching, 66 

top of front, 67 

views, definition, 66 
Outside diameter, measuring of, 270 

Paper 

blueprint, 166 

coordinate, 263 

drawing, 15, 119 

to fasten to the board, 15 

tracing, 166 
Partial view, 228 
Pen 

bow, 171 

care of. 169 

filling, 167 

ruling, 167 
Pencil 

drawing, 16 

lettering, 28 

review questions, pencil mechanical 
drawing, 154 

to sharpen, 17 
Pencils 

manipulation, 126 

requisites of, 125 



Perspective 

concentric circles in, 48 

direction of lines in, 11 

horizontal measurements in, 34 

measure cube in new positions, 57 

measure cylinder in new positions, 58 

measurements in, 31 

review questions, perspective sketch- 
ing, 61 

sketch, definition of, 10 

the cube in, 13 

the measure cube in, 34 

the table line. 35 
• to center sketch on sheet, 40 
Perspective sketching 

constructive stage in, 18 . 

enclosing solid in, 34 

finishing stage in, 18 

materials for, 15 
Pipe threads, 255 
Pitch 

of thread, 249 
Plane surfaces, representation of, 68 
Problems 

three view, 110 
Proportional inch scale, 128 

Quarter section. 99 

Radii, measuring. 278 
Radius dimensions, 150 
Rectangle 

border, 133 

enclosing, 133 
Rule, folding, 265 
Ruling horizontal lines, 126 
Ruling pen 

adjustment of, 167 

care of, 169 

filling, 168 

manipulation of, 168 

requisites of, 167 

sharpening, 169 
Ruling vertical lines, 126 

Scale 

of levels, cylindrical, 45 

of levels, rectangular, 31 

steel, 265 
Scales ' 

architect's, 127 

engineer's, 127 

proportional inch. 128 
Screw 

cap, 258 

machine, 25S 

.?et, 258 

wood screws, 231 



332 



INDEX 



Screw threads 

acme, 253 

pipe, 255 

square, 253 

U. S. Standard, 252 

V-Thread, 250 
Sectional views, 227 

breaks, 229 

brolven line, 228 

half section, 98 

partial, 228 

quarter section, 99 

revolved section, 228 

section through ribs, shafts, bolts, 
228 

separate section, 229 
Section lining, 171 
Set screws, 258 
Sharpening pencil, 17 
Shield, erasing, 132 
Sketch, perspective 

constructive stage, 18 

finishing stage,' 18 

perspective, definition of, 10 

to center on sheet, 40 
Sketching 

a circle, 101 

from the object, 261 

orthographic, 66 
Springs, 255 
Square 

adjustable, 266 

T-, 119 

threads, 253 
Straight edges, 69 
Strokes 

curved, 87 

horizontal in lettering, 55 

inclined in lettering, 189 

vertical in lettering, 55 
Strokes 

in lettering, 28 

in lettering, order, number, and di- 
rection of, 23, 28 
Stud, 258 
Stud bolt. 258 
Sub-title, 279 
Surfaces 

cylindrical, representation of, 92 

cylinder and cone, 223 

development of a surface, definition 
of, 189 

inclined, 81 



intersection of surfaces, 215 
plane, representation of, 68 
prism and cylinder, 217 
two cylinders, 220 

Table line, 35 
Tacks, thumb, 16 
Tangencies 

construction of, 325 

locating points of, 184 
Tap bolt. 258 
Thread 

multiple, 258 

pipe, 255 

screw, 249 (See Screw Threads) 
Three view problems. 110 
Thumb tacks, 1(5 
Title, block, 138 
Title, sub, 279 
Titles 

balance, 27, 140 

commercial, 139 

contents of, 139 

design of, 26 

steps in design, 26 

trial sheet, 140 
Tracing 

cloth, 161, 165 

paper, 166 

tracing and blueprinting, 185 

trimming the, 173 
Triangles 

use of, 121 

combination of, 124 

direction of drawing lines. 124 

testing, 122 

30° to 60°, 122 

45°, 122 

T-square, 119 

U. S. Standard thread, 252 

Vanishing points, definition of, 11 
Vertical lines, ruling, 126 
Views 

arrangement on sheet, 140 

definition of, 66 

partial, 228 

relation of front and side, 81 

relation of top and front, 67 

sectional, 227 




019 9453178 



